# Copyright 2021 Google Research The HuggingFace Inc. team. All rights reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""PyTorch BigBirdPegasus model."""

import math
from collections.abc import Callable

import numpy as np
import torch
from torch import nn
from torch.nn import BCEWithLogitsLoss, CrossEntropyLoss, MSELoss

from ... import initialization as init
from ...activations import ACT2FN
from ...cache_utils import Cache, DynamicCache, EncoderDecoderCache
from ...generation import GenerationMixin
from ...masking_utils import create_bidirectional_mask, create_causal_mask
from ...modeling_flash_attention_utils import FlashAttentionKwargs
from ...modeling_layers import GradientCheckpointingLayer
from ...modeling_outputs import (
    BaseModelOutput,
    BaseModelOutputWithPastAndCrossAttentions,
    CausalLMOutputWithCrossAttentions,
    Seq2SeqLMOutput,
    Seq2SeqModelOutput,
    Seq2SeqQuestionAnsweringModelOutput,
    Seq2SeqSequenceClassifierOutput,
)
from ...modeling_utils import ALL_ATTENTION_FUNCTIONS, PreTrainedModel
from ...processing_utils import Unpack
from ...utils import (
    TransformersKwargs,
    auto_docstring,
    can_return_tuple,
    is_torchdynamo_compiling,
    logging,
    torch_compilable_check,
)
from ...utils.generic import merge_with_config_defaults
from ...utils.output_capturing import OutputRecorder, capture_outputs
from .configuration_bigbird_pegasus import BigBirdPegasusConfig


logger = logging.get_logger(__name__)

_EXPECTED_OUTPUT_SHAPE = [1, 7, 1024]


def shift_tokens_right(input_ids: torch.Tensor, pad_token_id: int, decoder_start_token_id: int):
    """
    Shift input ids one token to the right.
    """
    shifted_input_ids = input_ids.new_zeros(input_ids.shape)
    shifted_input_ids[:, 1:] = input_ids[:, :-1].clone()
    shifted_input_ids[:, 0] = decoder_start_token_id

    if pad_token_id is None:
        raise ValueError("self.model.config.pad_token_id has to be defined.")
    # replace possible -100 values in labels by `pad_token_id`
    shifted_input_ids.masked_fill_(shifted_input_ids == -100, pad_token_id)

    return shifted_input_ids


class BigBirdPegasusLearnedPositionalEmbedding(nn.Embedding):
    """
    This module learns positional embeddings up to a fixed maximum size.
    """

    def __init__(self, num_embeddings: int, embedding_dim: int):
        super().__init__(num_embeddings, embedding_dim)

    def forward(
        self, input_ids_shape: torch.Size, past_key_values_length: int = 0, position_ids: torch.Tensor | None = None
    ):
        """`input_ids' shape is expected to be [bsz x seqlen]."""

        if position_ids is None:
            bsz, seq_len = input_ids_shape[:2]
            position_ids = torch.arange(
                past_key_values_length, past_key_values_length + seq_len, dtype=torch.long, device=self.weight.device
            )
        return super().forward(position_ids)


# Copied from transformers.models.bart.modeling_bart.BartScaledWordEmbedding with Bart->BigBirdPegasus
class BigBirdPegasusScaledWordEmbedding(nn.Embedding):
    """
    This module overrides nn.Embeddings' forward by multiplying with embeddings scale.
    """

    def __init__(self, num_embeddings: int, embedding_dim: int, padding_idx: int, embed_scale: float | None = 1.0):
        super().__init__(num_embeddings, embedding_dim, padding_idx)
        self.embed_scale = embed_scale

    def forward(self, input_ids: torch.Tensor):
        return super().forward(input_ids) * self.embed_scale


# Copied from transformers.models.big_bird.modeling_big_bird.BigBirdSelfAttention with BigBird->BigBirdPegasus
class BigBirdPegasusSelfAttention(nn.Module):
    def __init__(self, config, layer_idx=None):
        super().__init__()
        if config.hidden_size % config.num_attention_heads != 0 and not hasattr(config, "embedding_size"):
            raise ValueError(
                f"The hidden size ({config.hidden_size}) is not a multiple of the number of attention "
                f"heads ({config.num_attention_heads})"
            )

        self.num_attention_heads = config.num_attention_heads
        self.attention_head_size = int(config.hidden_size / config.num_attention_heads)
        self.all_head_size = self.num_attention_heads * self.attention_head_size

        self.query = nn.Linear(config.hidden_size, self.all_head_size, bias=config.use_bias)
        self.key = nn.Linear(config.hidden_size, self.all_head_size, bias=config.use_bias)
        self.value = nn.Linear(config.hidden_size, self.all_head_size, bias=config.use_bias)

        self.dropout = nn.Dropout(config.attention_probs_dropout_prob)
        self.is_decoder = config.is_decoder
        self.layer_idx = layer_idx

    def forward(
        self,
        hidden_states,
        attention_mask=None,
        encoder_hidden_states=None,
        encoder_attention_mask=None,
        past_key_values=None,
        **kwargs: Unpack[TransformersKwargs],
    ):
        batch_size, seq_length, _ = hidden_states.shape
        query_layer = (
            self.query(hidden_states)
            .view(batch_size, -1, self.num_attention_heads, self.attention_head_size)
            .transpose(1, 2)
        )

        is_cross_attention = encoder_hidden_states is not None
        current_states = encoder_hidden_states if is_cross_attention else hidden_states
        attention_mask = encoder_attention_mask if is_cross_attention else attention_mask
        if is_cross_attention and past_key_values is not None and past_key_values.get_seq_length(self.layer_idx) > 0:
            # reuse k,v, cross_attentions
            key_layer = past_key_values.layers[self.layer_idx].keys
            value_layer = past_key_values.layers[self.layer_idx].values
        else:
            key_layer = (
                self.key(current_states)
                .view(batch_size, -1, self.num_attention_heads, self.attention_head_size)
                .transpose(1, 2)
            )
            value_layer = (
                self.value(current_states)
                .view(batch_size, -1, self.num_attention_heads, self.attention_head_size)
                .transpose(1, 2)
            )

            if past_key_values is not None:
                # save all key/value_layer to cache to be re-used for fast auto-regressive generation
                key_layer, value_layer = past_key_values.update(
                    key_layer,
                    value_layer,
                    self.layer_idx,
                )

        # Take the dot product between "query" and "key" to get the raw attention scores.
        attention_scores = torch.matmul(query_layer, key_layer.transpose(-1, -2))

        attention_scores = attention_scores / math.sqrt(self.attention_head_size)
        if attention_mask is not None:
            # Apply the attention mask is (precomputed for all layers in BigBirdPegasusModel forward() function)
            attention_scores = attention_scores + attention_mask

        # Normalize the attention scores to probabilities.
        attention_probs = nn.functional.softmax(attention_scores, dim=-1)

        # This is actually dropping out entire tokens to attend to, which might
        # seem a bit unusual, but is taken from the original Transformer paper.
        attention_probs = self.dropout(attention_probs)

        context_layer = torch.matmul(attention_probs, value_layer)

        context_layer = context_layer.permute(0, 2, 1, 3).contiguous()
        new_context_layer_shape = context_layer.size()[:-2] + (self.all_head_size,)
        context_layer = context_layer.view(*new_context_layer_shape)

        return context_layer, attention_probs


# Copied from transformers.models.big_bird.modeling_big_bird.BigBirdBlockSparseAttention with BigBird->BigBirdPegasus
class BigBirdPegasusBlockSparseAttention(nn.Module):
    def __init__(self, config, seed=None):
        super().__init__()

        self.max_seqlen = config.max_position_embeddings
        self.seed = seed

        if config.hidden_size % config.num_attention_heads != 0:
            raise ValueError(
                f"The hidden size {config.hidden_size} is not a multiple of the number of attention "
                f"heads {config.num_attention_heads}."
            )

        self.num_attention_heads = config.num_attention_heads
        self.num_random_blocks = config.num_random_blocks
        self.block_size = config.block_size

        self.attention_head_size = int(config.hidden_size / config.num_attention_heads)
        self.all_head_size = self.num_attention_heads * self.attention_head_size

        self.query = nn.Linear(config.hidden_size, self.all_head_size, bias=config.use_bias)
        self.key = nn.Linear(config.hidden_size, self.all_head_size, bias=config.use_bias)
        self.value = nn.Linear(config.hidden_size, self.all_head_size, bias=config.use_bias)

    def forward(
        self,
        hidden_states,
        band_mask=None,
        from_mask=None,
        to_mask=None,
        from_blocked_mask=None,
        to_blocked_mask=None,
        **kwargs: Unpack[TransformersKwargs],
    ):
        batch_size, seqlen, _ = hidden_states.size()
        to_seq_length = from_seq_length = seqlen
        from_block_size = to_block_size = self.block_size

        if from_seq_length % from_block_size != 0:
            raise ValueError("Query sided sequence length must be multiple of block size")

        if to_seq_length % to_block_size != 0:
            raise ValueError("Key/Value sided sequence length must be multiple of block size")

        query_layer = (
            self.query(hidden_states)
            .view(batch_size, -1, self.num_attention_heads, self.attention_head_size)
            .transpose(1, 2)
        )
        key_layer = (
            self.key(hidden_states)
            .view(batch_size, -1, self.num_attention_heads, self.attention_head_size)
            .transpose(1, 2)
        )
        value_layer = (
            self.value(hidden_states)
            .view(batch_size, -1, self.num_attention_heads, self.attention_head_size)
            .transpose(1, 2)
        )

        context_layer, attention_probs = self.bigbird_block_sparse_attention(
            query_layer,
            key_layer,
            value_layer,
            band_mask,
            from_mask,
            to_mask,
            from_blocked_mask,
            to_blocked_mask,
            self.num_attention_heads,
            self.num_random_blocks,
            self.attention_head_size,
            from_block_size,
            to_block_size,
            batch_size,
            from_seq_length,
            to_seq_length,
            seed=self.seed,
            plan_from_length=None,
            plan_num_rand_blocks=None,
        )

        context_layer = context_layer.contiguous().view(batch_size, from_seq_length, -1)
        return context_layer, attention_probs

    @staticmethod
    def torch_bmm_nd(inp_1, inp_2, ndim=None):
        """Fast nd matrix multiplication"""
        # faster replacement of torch.einsum ("bhqk,bhkd->bhqd")
        return torch.bmm(inp_1.reshape((-1,) + inp_1.shape[-2:]), inp_2.reshape((-1,) + inp_2.shape[-2:])).view(
            inp_1.shape[: ndim - 2] + (inp_1.shape[ndim - 2], inp_2.shape[ndim - 1])
        )

    @staticmethod
    def torch_bmm_nd_transpose(inp_1, inp_2, ndim=None):
        """Fast nd matrix multiplication with transpose"""
        # faster replacement of torch.einsum (bhqd,bhkd->bhqk)
        return torch.bmm(
            inp_1.reshape((-1,) + inp_1.shape[-2:]), inp_2.reshape((-1,) + inp_2.shape[-2:]).transpose(1, 2)
        ).view(inp_1.shape[: ndim - 2] + (inp_1.shape[ndim - 2], inp_2.shape[ndim - 2]))

    def bigbird_block_sparse_attention(
        self,
        query_layer,
        key_layer,
        value_layer,
        band_mask,
        from_mask,
        to_mask,
        from_blocked_mask,
        to_blocked_mask,
        n_heads,
        n_rand_blocks,
        attention_head_size,
        from_block_size,
        to_block_size,
        batch_size,
        from_seq_len,
        to_seq_len,
        seed,
        plan_from_length,
        plan_num_rand_blocks,
    ):
        # BigBirdPegasus block-sparse attention as suggested in paper

        # ITC:
        #     global tokens: 2 x block_size
        #     window tokens: 3 x block_size
        #     random tokens: num_rand_tokens x block_size

        # ETC:
        #     global tokens: extra_globals_tokens + 2 x block_size
        #     window tokens: 3 x block_size
        #     random tokens: num_rand_tokens x block_size

        # Note:
        #     1) Currently, ETC is not supported.
        #     2) Window size is fixed to 3 blocks & it can be changed only by
        #     changing `block_size`.
        #     3) Number of global blocks are fixed (2 blocks here) & global tokens can be
        #     controlled only by `block_size`.

        # attention is calculated separately for q[0], q[1], q[2:-2], q[-2], q[-1] in order to use special trick of shifting tokens (for calculating sliding attention)
        # hence following code can be divided into 5 parts.

        if from_seq_len // from_block_size != to_seq_len // to_block_size:
            raise ValueError("Error the number of blocks needs to be same!")

        rsqrt_d = 1 / math.sqrt(attention_head_size)
        bsz = batch_size
        attn_mask_penalty = -10000.0

        # generate random attention and corresponding masks
        np.random.seed(seed)
        if from_seq_len in [1024, 3072, 4096]:  # old plans used in paper
            rand_attn = [
                self._bigbird_block_rand_mask(
                    self.max_seqlen, self.max_seqlen, from_block_size, to_block_size, n_rand_blocks, last_idx=1024
                )[: (from_seq_len // from_block_size - 2)]
                for _ in range(n_heads)
            ]
        else:
            if plan_from_length is None:
                plan_from_length, plan_num_rand_blocks = self._get_rand_attn_plan(
                    from_seq_len, from_block_size, n_rand_blocks
                )

            rand_attn = self._bigbird_block_rand_mask_with_head(
                from_seq_length=from_seq_len,
                to_seq_length=to_seq_len,
                from_block_size=from_block_size,
                to_block_size=to_block_size,
                num_heads=n_heads,
                plan_from_length=plan_from_length,
                plan_num_rand_blocks=plan_num_rand_blocks,
            )

        rand_attn = np.stack(rand_attn, axis=0)
        rand_attn = torch.tensor(rand_attn, device=query_layer.device, dtype=torch.long)
        rand_attn.unsqueeze_(0)
        rand_attn = torch.cat([rand_attn for _ in range(batch_size)], dim=0)

        rand_mask = self._create_rand_mask_from_inputs(
            from_blocked_mask, to_blocked_mask, rand_attn, n_heads, n_rand_blocks, bsz, from_seq_len, from_block_size
        )

        blocked_query_matrix = query_layer.view(bsz, n_heads, from_seq_len // from_block_size, from_block_size, -1)
        blocked_key_matrix = key_layer.view(bsz, n_heads, to_seq_len // to_block_size, to_block_size, -1)
        blocked_value_matrix = value_layer.view(bsz, n_heads, to_seq_len // to_block_size, to_block_size, -1)

        # preparing block for randn attn
        gathered_key = self.torch_gather_b2(blocked_key_matrix, rand_attn)
        gathered_key = gathered_key.view(
            bsz, n_heads, to_seq_len // to_block_size - 2, n_rand_blocks * to_block_size, -1
        )  # [bsz, n_heads, to_seq_len//to_block_size-2, n_rand_blocks, to_block_size, -1]
        gathered_value = self.torch_gather_b2(blocked_value_matrix, rand_attn)
        gathered_value = gathered_value.view(
            bsz, n_heads, to_seq_len // to_block_size - 2, n_rand_blocks * to_block_size, -1
        )  # [bsz, n_heads, to_seq_len//to_block_size-2, n_rand_blocks, to_block_size, -1]

        # 1st PART
        # 1st block (global block) attention scores
        # q[0] x (k[0], k[1], k[2], k[3], k[4] .... )

        # [bsz, n_heads, from_block_size, -1] x [bsz, n_heads, to_seq_len, -1] ==> [bsz, n_heads, from_block_size, to_seq_len]
        first_product = self.torch_bmm_nd_transpose(blocked_query_matrix[:, :, 0], key_layer, ndim=4)

        first_product = first_product * rsqrt_d
        first_product += (1.0 - to_mask) * attn_mask_penalty
        first_attn_weights = nn.functional.softmax(
            first_product, dim=-1
        )  # [bsz, n_heads, from_block_size, to_seq_len]

        # [bsz, n_heads, from_block_size, to_seq_len] x [bsz, n_heads, to_seq_len, -1] ==> [bsz, n_heads, from_block_size, -1]
        first_context_layer = self.torch_bmm_nd(first_attn_weights, value_layer, ndim=4)
        first_context_layer.unsqueeze_(2)

        # 2nd PART
        # 2nd block attention scores
        # q[1] x (sliding_keys, random_keys, global_keys)
        # sliding key blocks -> 2nd, 3rd blocks
        # global key blocks -> 1st block

        second_key_mat = torch.cat(
            [
                blocked_key_matrix[:, :, 0],
                blocked_key_matrix[:, :, 1],
                blocked_key_matrix[:, :, 2],
                blocked_key_matrix[:, :, -1],
                gathered_key[:, :, 0],
            ],
            dim=2,
        )  # [bsz, n_heads, (4+n_rand_blocks)*to_block_size, -1]
        second_value_mat = torch.cat(
            [
                blocked_value_matrix[:, :, 0],
                blocked_value_matrix[:, :, 1],
                blocked_value_matrix[:, :, 2],
                blocked_value_matrix[:, :, -1],
                gathered_value[:, :, 0],
            ],
            dim=2,
        )  # [bsz, n_heads, (4+n_rand_blocks)*to_block_size, -1]

        # [bsz, n_heads, from_block_size, -1] x [bsz, n_heads, (4+n_rand_blocks)*to_block_size, -1] ==> [bsz, n_heads, from_block_size, (4+n_rand_blocks)*to_block_size]
        second_product = self.torch_bmm_nd_transpose(blocked_query_matrix[:, :, 1], second_key_mat, ndim=4)
        second_seq_pad = torch.cat(
            [
                to_mask[:, :, :, : 3 * to_block_size],
                to_mask[:, :, :, -to_block_size:],
                to_mask.new_ones([bsz, 1, 1, n_rand_blocks * to_block_size]),
            ],
            dim=3,
        )
        second_rand_pad = torch.cat(
            [
                rand_mask.new_ones([bsz, n_heads, from_block_size, 4 * to_block_size]),
                rand_mask[:, :, 0],
            ],
            dim=3,
        )
        second_product = second_product * rsqrt_d
        second_product += (1.0 - torch.minimum(second_seq_pad, second_rand_pad)) * attn_mask_penalty
        second_attn_weights = nn.functional.softmax(
            second_product, dim=-1
        )  # [bsz, n_heads, from_block_size, (4+n_rand_blocks)*to_block_size]

        # [bsz, n_heads, from_block_size, (4+n_rand_blocks)*to_block_size] x [bsz, n_heads, (4+n_rand_blocks)*to_block_size, -1] ==> [bsz, n_heads, from_block_size, -1]
        second_context_layer = self.torch_bmm_nd(second_attn_weights, second_value_mat, ndim=4)

        second_context_layer.unsqueeze_(2)

        # 3rd PART
        # Middle blocks attention scores
        # q[-2:2] x (sliding_keys, random_keys, global_keys)
        # sliding attn is calculated using special trick of shifting tokens as discussed in paper
        # random keys are generated by taking random indices as per `rand_attn`
        # global keys -> 1st & last block

        exp_blocked_key_matrix = torch.cat(
            [blocked_key_matrix[:, :, 1:-3], blocked_key_matrix[:, :, 2:-2], blocked_key_matrix[:, :, 3:-1]], dim=3
        )  # [bsz, n_heads, from_seq_len//from_block_size-4, 3*to_block_size, -1]
        exp_blocked_value_matrix = torch.cat(
            [blocked_value_matrix[:, :, 1:-3], blocked_value_matrix[:, :, 2:-2], blocked_value_matrix[:, :, 3:-1]],
            dim=3,
        )  # [bsz, n_heads, from_seq_len//from_block_size-4, 3*to_block_size, -1]
        middle_query_matrix = blocked_query_matrix[:, :, 2:-2]

        # sliding attention scores for q[-2:2]
        # [bsz, n_heads, from_seq_len//from_block_size-4, from_block_size, -1] x [b, n_heads, from_seq_len//from_block_size-4, 3*to_block_size, -1]
        inner_band_product = self.torch_bmm_nd_transpose(middle_query_matrix, exp_blocked_key_matrix, ndim=5)
        #     ==> [bsz, n_heads, from_seq_len//from_block_size-4, from_block_size, 3*to_block_size]
        inner_band_product = inner_band_product * rsqrt_d

        # randn attention scores for q[-2:2]
        # [bsz, n_heads, from_seq_len//from_block_size-4, from_block_size, -1] x [bsz, n_heads, from_seq_len//from_block_size-4, n_rand_blocks*to_block_size, -1]
        rand_band_product = self.torch_bmm_nd_transpose(middle_query_matrix, gathered_key[:, :, 1:-1], ndim=5)
        #     ==> [bsz, n_heads, from_seq_len//from_block_size-4, from_block_size, n_rand_blocks*to_block_size]
        rand_band_product = rand_band_product * rsqrt_d

        # Including 1st block (since it's global)
        first_band_product = torch.einsum(
            "bhlqd,bhkd->bhlqk", middle_query_matrix, blocked_key_matrix[:, :, 0]
        )  # [bsz, n_heads, from_seq_len//from_block_size-4, from_block_size, -1] x [bsz, n_heads, to_block_size, -1] ==> [bsz, n_heads, from_seq_len//from_block_size-4, from_block_size, to_block_size]
        first_band_product = first_band_product * rsqrt_d

        # Including last block (since it's global)
        last_band_product = torch.einsum(
            "bhlqd,bhkd->bhlqk", middle_query_matrix, blocked_key_matrix[:, :, -1]
        )  # [bsz, n_heads, from_seq_len//from_block_size-4, from_block_size, -1] x [bsz, n_heads, to_block_size, -1] ==> [bsz, n_heads, from_seq_len//from_block_size-4, from_block_size, to_block_size]
        last_band_product = last_band_product * rsqrt_d

        # masking padded tokens
        inner_band_product += (1.0 - band_mask) * attn_mask_penalty
        first_band_product += (1.0 - to_mask[:, :, :, :to_block_size].unsqueeze(3)) * attn_mask_penalty
        last_band_product += (1.0 - to_mask[:, :, :, -to_block_size:].unsqueeze(3)) * attn_mask_penalty
        rand_band_product += (1.0 - rand_mask[:, :, 1:-1]) * attn_mask_penalty

        # completing attention scores matrix for all q[-2:2]
        band_product = torch.cat(
            [first_band_product, inner_band_product, rand_band_product, last_band_product], dim=-1
        )  # [bsz, n_heads, from_seq_len//from_block_size-4, from_block_size, (5+n_rand_blocks)*to_block_size]

        # safely doing softmax since attention matrix is completed
        attn_weights = nn.functional.softmax(
            band_product, dim=-1
        )  # [bsz, n_heads, from_seq_len//from_block_size-4, from_block_size, (5+n_rand_blocks)*to_block_size]

        # contribution of sliding keys
        # [bsz, n_heads, m//from_block_size-4, from_block_size, 3*to_block_size] x [bsz, n_heads, from_seq_len//from_block_size-4, 3*to_block_size, -1]
        context_layer = self.torch_bmm_nd(
            attn_weights[:, :, :, :, to_block_size : 4 * to_block_size], exp_blocked_value_matrix, ndim=5
        )
        #     ==> [bsz, n_heads, from_seq_len//from_block_size-4, from_block_size, -1]

        # adding contribution of random keys
        # [bsz, n_heads, from_seq_len//from_block_size-4, from_block_size, n_rand_blocks*to_block_size] x [bsz, n_heads, from_seq_len//from_block_size-4, n_rand_blocks*to_block_size, -1]
        context_layer += self.torch_bmm_nd(
            attn_weights[:, :, :, :, 4 * to_block_size : -to_block_size], gathered_value[:, :, 1:-1], ndim=5
        )
        #     ==> [bsz, n_heads, from_seq_len//from_block_size-4, from_block_size, -1]

        # adding contribution of global keys
        context_layer += torch.einsum(
            "bhlqk,bhkd->bhlqd", attn_weights[:, :, :, :, :to_block_size], blocked_value_matrix[:, :, 0]
        )  # [bsz, n_heads, from_seq_len//from_block_size-4, from_block_size, to_block_size] x [bsz, n_heads, to_block_size, -1] ==> [bsz, n_heads, from_seq_len//from_block_size-4, from_block_size, -1]
        context_layer += torch.einsum(
            "bhlqk,bhkd->bhlqd", attn_weights[:, :, :, :, -to_block_size:], blocked_value_matrix[:, :, -1]
        )  # [bsz, n_heads, from_seq_len//from_block_size-4, from_block_size, to_block_size] x [bsz, n_heads, to_block_size, -1] ==> [bsz, n_heads, from_seq_len//from_block_size-4, from_block_size, -1]

        # 4th PART
        # last 2nd token attention scores
        # q[-2] x (sliding_keys, random_keys, global_keys)
        # sliding key blocks -> last 3 blocks
        # global key block -> 1st block
        # random key block -> based on indices stored in `randn_attn`

        second_last_key_mat = torch.cat(
            [
                blocked_key_matrix[:, :, 0],
                blocked_key_matrix[:, :, -3],
                blocked_key_matrix[:, :, -2],
                blocked_key_matrix[:, :, -1],
                gathered_key[:, :, -1],
            ],
            dim=2,
        )  # [bsz, n_heads, (4+n_random_blocks)*to_block_size, -1]
        second_last_value_mat = torch.cat(
            [
                blocked_value_matrix[:, :, 0],
                blocked_value_matrix[:, :, -3],
                blocked_value_matrix[:, :, -2],
                blocked_value_matrix[:, :, -1],
                gathered_value[:, :, -1],
            ],
            dim=2,
        )  # [bsz, n_heads, (4+r)*to_block_size, -1]

        # [bsz, n_heads, from_block_size, -1] x [bsz, n_heads, (4+n_rand_blocks)*to_block_size, -1] ==> [bsz, n_heads, from_block_size, (4+n_rand_blocks)*to_block_size]
        second_last_product = self.torch_bmm_nd_transpose(blocked_query_matrix[:, :, -2], second_last_key_mat, ndim=4)
        second_last_seq_pad = torch.cat(
            [
                to_mask[:, :, :, :to_block_size],
                to_mask[:, :, :, -3 * to_block_size :],
                to_mask.new_ones([bsz, 1, 1, n_rand_blocks * to_block_size]),
            ],
            dim=3,
        )
        second_last_rand_pad = torch.cat(
            [
                rand_mask.new_ones([bsz, n_heads, from_block_size, 4 * to_block_size]),
                rand_mask[:, :, -1],
            ],
            dim=3,
        )
        second_last_product = second_last_product * rsqrt_d
        second_last_product += (1.0 - torch.minimum(second_last_seq_pad, second_last_rand_pad)) * attn_mask_penalty
        second_last_attn_weights = nn.functional.softmax(
            second_last_product, dim=-1
        )  # [bsz, n_heads, from_block_size, (4+n_rand_blocks)*to_block_size]

        # [bsz, n_heads, from_block_size, (4+n_rand_blocks)*to_block_size] x [bsz, n_heads, (4+n_rand_blocks)*to_block_size, -1] ==> [bsz, n_heads, from_block_size, -1]
        second_last_context_layer = self.torch_bmm_nd(second_last_attn_weights, second_last_value_mat, ndim=4)
        second_last_context_layer.unsqueeze_(2)

        # 5th PART
        # last block (global) attention scores
        # q[-1] x (k[0], k[1], k[2], k[3], .... )

        # [bsz, n_heads, from_block_size, -1] x [bsz, n_heads, to_seq_len, -1] ==> [bsz, n_heads, from_block_size, to_seq_len]
        last_product = self.torch_bmm_nd_transpose(blocked_query_matrix[:, :, -1], key_layer, ndim=4)
        last_product = last_product * rsqrt_d
        last_product += (1.0 - to_mask) * attn_mask_penalty
        last_attn_weights = nn.functional.softmax(last_product, dim=-1)  # [bsz, n_heads, from_block_size, n]

        # [bsz, n_heads, from_block_size, to_seq_len] x [bsz, n_heads, to_seq_len, -1] ==> [bsz, n_heads, from_block_size, -1]
        last_context_layer = self.torch_bmm_nd(last_attn_weights, value_layer, ndim=4)
        last_context_layer.unsqueeze_(2)

        # combining representations of all tokens
        context_layer = torch.cat(
            [first_context_layer, second_context_layer, context_layer, second_last_context_layer, last_context_layer],
            dim=2,
        )
        context_layer = context_layer.view((bsz, n_heads, from_seq_len, -1)) * from_mask
        context_layer = torch.transpose(context_layer, 1, 2)

        # this is just for visualizing; forward pass doesn't depend on following code
        # TODO(PVP): need to verify if below code is correct
        attention_probs = torch.zeros(
            bsz, n_heads, from_seq_len, to_seq_len, dtype=context_layer.dtype, device=context_layer.device
        )

        # 1st query block
        # corresponding to `first_context_layer`
        attention_probs[:, :, :from_block_size, :] = first_attn_weights  # all keys global

        # 2nd query block
        # corresponding to `second_context_layer`
        attention_probs[:, :, from_block_size : 2 * from_block_size, : 3 * to_block_size] = second_attn_weights[
            :, :, :, : 3 * to_block_size
        ]  # 1st three key blocks (global + sliding)
        attention_probs[:, :, from_block_size : 2 * from_block_size, -to_block_size:] = second_attn_weights[
            :, :, :, 3 * to_block_size : 4 * to_block_size
        ]  # last key block (global)
        # random keys
        for p1, i1, w1 in zip(range(bsz), rand_attn, second_attn_weights):
            # p1, i1, w1 corresponds to batch_dim i.e. following operation is done for each sequence in batch
            for p2, i2, w2 in zip(range(n_heads), i1, w1):
                # p2, i2, w2 corresponds to head_dim i.e. following operation is done for each heads
                attn_probs_view = attention_probs.view(
                    bsz,
                    n_heads,
                    from_seq_len // from_block_size,
                    from_block_size,
                    to_seq_len // to_block_size,
                    to_block_size,
                )
                right_slice = w2[:, 4 * to_block_size :]
                attn_probs_view[p1, p2, 1, :, i2[0]] = right_slice.view(from_block_size, n_rand_blocks, to_block_size)

        # Middle query blocks
        # corresponding to `context_layer`
        # sliding keys
        for q_idx in range(from_seq_len // from_block_size - 4):
            attn_probs_view = attention_probs.view(
                bsz,
                n_heads,
                from_seq_len // from_block_size,
                from_block_size,
                to_seq_len // to_block_size,
                to_block_size,
            )[:, :, 2:-2, :, 1:-1, :]
            right_slice = attn_weights[:, :, q_idx, :, to_block_size : 4 * to_block_size]
            attn_probs_view[:, :, q_idx, :, q_idx : q_idx + 3, :] = right_slice.view(
                bsz, n_heads, from_block_size, 3, to_block_size
            )  # inner_band_product
        # global keys (corresponding to 1st key block)
        attention_probs[:, :, 2 * from_block_size : -2 * from_block_size, :to_block_size] = attn_weights[
            :, :, :, :, :to_block_size
        ].view(bsz, n_heads, -1, to_block_size)  # first_band_product
        # global keys (corresponding to last key block)
        attention_probs[:, :, 2 * from_block_size : -2 * from_block_size, -to_block_size:] = attn_weights[
            :, :, :, :, -to_block_size:
        ].view(bsz, n_heads, -1, to_block_size)  # last_band_product
        # random keys
        for p1, i1, w1 in zip(range(bsz), rand_attn, attn_weights):
            # p1, i1, w1 corresponds to batch_dim i.e. following operation is done for each sequence in batch
            for p2, i2, w2 in zip(range(n_heads), i1, w1):
                # p2, i2, w2 corresponds to head_dim i.e. following operation is done for each heads
                for q_idx in range(1, len(i2) - 1):
                    attn_probs_view = attention_probs.view(
                        bsz,
                        n_heads,
                        from_seq_len // from_block_size,
                        from_block_size,
                        to_seq_len // to_block_size,
                        to_block_size,
                    )
                    right_slice = w2[q_idx - 1, :, 4 * to_block_size : -to_block_size]
                    attn_probs_view[p1, p2, q_idx + 1, :, i2[q_idx]] = right_slice.view(
                        from_block_size, n_rand_blocks, to_block_size
                    )

        # Second-last query block
        # corresponding to `second_last_context_layer`
        attention_probs[:, :, -2 * from_block_size : -from_block_size, :to_block_size] = second_last_attn_weights[
            :, :, :, :to_block_size
        ]  # 1st key block (global)
        attention_probs[:, :, -2 * from_block_size : -from_block_size, -3 * to_block_size :] = (
            second_last_attn_weights[:, :, :, to_block_size : 4 * to_block_size]
        )  # last three blocks (global + sliding)
        # random keys
        for p1, i1, w1 in zip(range(bsz), rand_attn, second_last_attn_weights):
            # p1, i1, w1 corresponds to batch_dim i.e. following operation is done for each sequence in batch
            for p2, i2, w2 in zip(range(n_heads), i1, w1):
                # p2, i2, w2 corresponds to head_dim i.e. following operation is done for each heads
                attn_probs_view = attention_probs.view(
                    bsz,
                    n_heads,
                    from_seq_len // from_block_size,
                    from_block_size,
                    to_seq_len // to_block_size,
                    to_block_size,
                )
                right_slice = w2[:, 4 * to_block_size :]
                attn_probs_view[p1, p2, -2, :, i2[-1]] = right_slice.view(
                    from_block_size, n_rand_blocks, to_block_size
                )

        # last query block
        # corresponding to `last_context_layer`
        attention_probs[:, :, -from_block_size:, :] = last_attn_weights  # all keys global

        return context_layer, attention_probs

    @staticmethod
    def torch_gather_b2(params, indices):
        if params.shape[:2] != indices.shape[:2]:
            raise ValueError(
                "Make sure that the first two dimensions of params and indices are identical,                 but"
                f" they are params: {params.shape[:2]} vs. indices: {indices.shape[:2]}"
            )
        num_indices_to_gather = indices.shape[-2] * indices.shape[-1]
        num_indices_to_pick_from = params.shape[2]

        shift = torch.arange(indices.shape[0] * indices.shape[1] * num_indices_to_gather, device=indices.device)
        indices_shift = torch.div(shift, num_indices_to_gather, rounding_mode="floor") * num_indices_to_pick_from

        flattened_indices = indices.view(-1) + indices_shift
        flattened_params = params.reshape(-1, params.shape[-2], params.shape[-1])

        out_flattened = flattened_params.index_select(0, flattened_indices)

        out = out_flattened.reshape(params.shape[:2] + (num_indices_to_gather,) + params.shape[3:])
        return out

    @staticmethod
    def _create_rand_mask_from_inputs(
        from_blocked_mask,
        to_blocked_mask,
        rand_attn,
        num_attention_heads,
        num_rand_blocks,
        batch_size,
        from_seq_length,
        from_block_size,
    ):
        """
        Create 3D attention mask from a 2D tensor mask.

        Args:
            from_blocked_mask: 2D Tensor of shape [batch_size,
            from_seq_length//from_block_size, from_block_size].
            to_blocked_mask: int32 Tensor of shape [batch_size,
            to_seq_length//to_block_size, to_block_size].
            rand_attn: [batch_size, num_attention_heads,
            from_seq_length//from_block_size-2, num_rand_blocks]
            num_attention_heads: int. Number of attention heads.
            num_rand_blocks: int. Number of random chunks per row.
            batch_size: int. Batch size for computation.
            from_seq_length: int. length of from sequence.
            from_block_size: int. size of block in from sequence.

        Returns:
            float Tensor of shape [batch_size, num_attention_heads, from_seq_length//from_block_size-2,
            from_block_size, num_rand_blocks*to_block_size].
        """
        num_windows = from_seq_length // from_block_size - 2
        rand_mask = torch.stack([p1[i1.flatten()] for p1, i1 in zip(to_blocked_mask, rand_attn)])
        rand_mask = rand_mask.view(batch_size, num_attention_heads, num_windows, num_rand_blocks * from_block_size)
        rand_mask = torch.einsum("blq,bhlk->bhlqk", from_blocked_mask[:, 1:-1], rand_mask)
        return rand_mask

    @staticmethod
    def _get_rand_attn_plan(from_seq_length, from_block_size, num_rand_blocks):
        """
        Gives the plan of where to put random attention.

        Args:
            from_seq_length: int. length of from sequence.
            from_block_size: int. size of block in from sequence.
            num_rand_blocks: int. Number of random chunks per row.

        Returns:
            plan_from_length: ending location of from block plan_num_rand_blocks: number of random ending location for
            each block
        """

        plan_from_length = []
        plan_num_rand_blocks = []
        if (2 * num_rand_blocks + 5) < (from_seq_length // from_block_size):
            plan_from_length.append(int((2 * num_rand_blocks + 5) * from_block_size))
            plan_num_rand_blocks.append(num_rand_blocks)
            plan_from_length.append(from_seq_length)
            plan_num_rand_blocks.append(0)
        elif (num_rand_blocks + 5) < (from_seq_length // from_block_size):
            plan_from_length.append(int((num_rand_blocks + 5) * from_block_size))
            plan_num_rand_blocks.append(num_rand_blocks // 2)
            plan_from_length.append(from_seq_length)
            plan_num_rand_blocks.append(num_rand_blocks - (num_rand_blocks // 2))
        else:
            plan_from_length.append(from_seq_length)
            plan_num_rand_blocks.append(num_rand_blocks)

        return plan_from_length, plan_num_rand_blocks

    def _bigbird_block_rand_mask(
        self, from_seq_length, to_seq_length, from_block_size, to_block_size, num_rand_blocks, last_idx=-1
    ):
        """
        Create adjacency list of random attention.

        Args:
            from_seq_length: int. length of from sequence.
            to_seq_length: int. length of to sequence.
            from_block_size: int. size of block in from sequence.
            to_block_size: int. size of block in to sequence.
            num_rand_blocks: int. Number of random chunks per row.
            last_idx: if -1 then num_rand_blocks blocks chosen anywhere in to sequence,
            if positive then num_rand_blocks blocks chosen only up to last_idx.

        Returns:
            adjacency list of size from_seq_length//from_block_size-2 by num_rand_blocks
        """
        # using this method when from_seq_length in [1024, 3072, 4096]

        if from_seq_length // from_block_size != to_seq_length // to_block_size:
            raise ValueError("Error the number of blocks needs to be same!")

        rand_attn = np.zeros((from_seq_length // from_block_size - 2, num_rand_blocks), dtype=np.int32)
        # During inference (eval) no randomness
        if not self.training:
            return rand_attn
        middle_seq = np.arange(1, to_seq_length // to_block_size - 1, dtype=np.int32)
        last = to_seq_length // to_block_size - 1
        if last_idx > (2 * to_block_size):
            last = (last_idx // to_block_size) - 1

        r = num_rand_blocks  # shorthand
        for i in range(1, from_seq_length // from_block_size - 1):
            start = i - 2
            end = i
            if i == 1:
                rand_attn[i - 1, :] = np.random.permutation(middle_seq[2:last])[:r]
            elif i == 2:
                rand_attn[i - 1, :] = np.random.permutation(middle_seq[3:last])[:r]
            elif i == from_seq_length // from_block_size - 3:
                rand_attn[i - 1, :] = np.random.permutation(middle_seq[:last])[:r]
            # Missing -3: should have been sliced till last-3
            elif i == from_seq_length // from_block_size - 2:
                rand_attn[i - 1, :] = np.random.permutation(middle_seq[:last])[:r]
            # Missing -4: should have been sliced till last-4
            else:
                if start > last:
                    start = last
                    rand_attn[i - 1, :] = np.random.permutation(middle_seq[:start])[:r]
                elif (end + 1) == last:
                    rand_attn[i - 1, :] = np.random.permutation(middle_seq[:start])[:r]
                else:
                    rand_attn[i - 1, :] = np.random.permutation(
                        np.concatenate((middle_seq[:start], middle_seq[end + 1 : last]))
                    )[:r]
        return rand_attn

    def _bigbird_block_rand_mask_with_head(
        self,
        from_seq_length,
        to_seq_length,
        from_block_size,
        to_block_size,
        num_heads,
        plan_from_length,
        plan_num_rand_blocks,
        window_block_left=1,
        window_block_right=1,
        global_block_top=1,
        global_block_bottom=1,
        global_block_left=1,
        global_block_right=1,
    ):
        """
        Create adjacency list of random attention.

        Args:
            from_seq_length: int. length of from sequence.
            to_seq_length: int. length of to sequence.
            from_block_size: int. size of block in from sequence.
            to_block_size: int. size of block in to sequence.
            num_heads: int. total number of heads.
            plan_from_length: list. plan from length where num_random_blocks are chosen from.
            plan_num_rand_blocks: list. number of rand blocks within the plan.
            window_block_left: int. number of blocks of window to left of a block.
            window_block_right: int. number of blocks of window to right of a block.
            global_block_top: int. number of blocks at the top.
            global_block_bottom: int. number of blocks at the bottom.
            global_block_left: int. Number of blocks globally used to the left.
            global_block_right: int. Number of blocks globally used to the right.

        Returns:
            adjacency list of size num_head where each element is of size from_seq_length//from_block_size-2 by
            num_rand_blocks
        """
        # using this method when from_seq_length not in [1024, 3072, 4096]

        if from_seq_length // from_block_size != to_seq_length // to_block_size:
            raise ValueError("Error the number of blocks needs to be same!")

        if from_seq_length not in plan_from_length:
            raise ValueError("Error from sequence length not in plan!")

        # Total number of blocks in the mmask
        num_blocks = from_seq_length // from_block_size
        # Number of blocks per plan
        plan_block_length = np.array(plan_from_length) // from_block_size
        # till when to follow plan
        max_plan_idx = plan_from_length.index(from_seq_length)

        # Random Attention adjacency list
        rand_attn = [
            np.zeros((num_blocks, np.sum(plan_num_rand_blocks[: max_plan_idx + 1])), dtype=np.int32)
            for i in range(num_heads)
        ]
        # During inference (eval) no randomness
        if not self.training:
            for nh in range(num_heads):
                rand_attn[nh] = rand_attn[nh][global_block_top : num_blocks - global_block_bottom, :]
            return rand_attn

        # We will go iteratively over the plan blocks and pick random number of
        # Attention blocks from the legally allowed blocks
        for plan_idx in range(max_plan_idx + 1):
            rnd_r_cnt = 0
            if plan_idx > 0:
                # set the row for all from_blocks starting from 0 to
                # plan_block_length[plan_idx-1]
                # column indx start from plan_block_length[plan_idx-1] and ends at
                # plan_block_length[plan_idx]
                if plan_num_rand_blocks[plan_idx] > 0:
                    rnd_r_cnt = int(np.sum(plan_num_rand_blocks[:plan_idx]))
                    curr_r_cnt = int(np.sum(plan_num_rand_blocks[: plan_idx + 1]))
                    for blk_rw_idx in range(global_block_top, plan_block_length[plan_idx - 1]):
                        for h in range(num_heads):
                            rand_attn[h][blk_rw_idx, rnd_r_cnt:curr_r_cnt] = self._get_single_block_row_attention(
                                block_id=blk_rw_idx,
                                to_start_block_id=plan_block_length[plan_idx - 1],
                                to_end_block_id=plan_block_length[plan_idx],
                                num_rand_blocks=plan_num_rand_blocks[plan_idx],
                                window_block_left=window_block_left,
                                window_block_right=window_block_right,
                                global_block_left=global_block_left,
                                global_block_right=global_block_right,
                            )

                for pl_id in range(plan_idx):
                    if plan_num_rand_blocks[pl_id] == 0:
                        continue
                    for blk_rw_idx in range(plan_block_length[plan_idx - 1], plan_block_length[plan_idx]):
                        rnd_r_cnt = 0
                        to_start_block_id = 0
                        if pl_id > 0:
                            rnd_r_cnt = int(np.sum(plan_num_rand_blocks[:pl_id]))
                            to_start_block_id = plan_block_length[pl_id - 1]
                        curr_r_cnt = int(np.sum(plan_num_rand_blocks[: pl_id + 1]))
                        for h in range(num_heads):
                            rand_attn[h][blk_rw_idx, rnd_r_cnt:curr_r_cnt] = self._get_single_block_row_attention(
                                block_id=blk_rw_idx,
                                to_start_block_id=to_start_block_id,
                                to_end_block_id=plan_block_length[pl_id],
                                num_rand_blocks=plan_num_rand_blocks[pl_id],
                                window_block_left=window_block_left,
                                window_block_right=window_block_right,
                                global_block_left=global_block_left,
                                global_block_right=global_block_right,
                            )

            if plan_num_rand_blocks[plan_idx] == 0:
                continue
            curr_r_cnt = int(np.sum(plan_num_rand_blocks[: plan_idx + 1]))
            from_start_block_id = global_block_top
            to_start_block_id = 0
            if plan_idx > 0:
                rnd_r_cnt = int(np.sum(plan_num_rand_blocks[:plan_idx]))
                from_start_block_id = plan_block_length[plan_idx - 1]
                to_start_block_id = plan_block_length[plan_idx - 1]

            for blk_rw_idx in range(from_start_block_id, plan_block_length[plan_idx]):
                for h in range(num_heads):
                    rand_attn[h][blk_rw_idx, rnd_r_cnt:curr_r_cnt] = self._get_single_block_row_attention(
                        block_id=blk_rw_idx,
                        to_start_block_id=to_start_block_id,
                        to_end_block_id=plan_block_length[plan_idx],
                        num_rand_blocks=plan_num_rand_blocks[plan_idx],
                        window_block_left=window_block_left,
                        window_block_right=window_block_right,
                        global_block_left=global_block_left,
                        global_block_right=global_block_right,
                    )

        for nh in range(num_heads):
            rand_attn[nh] = rand_attn[nh][global_block_top : num_blocks - global_block_bottom, :]

        return rand_attn

    @staticmethod
    def _get_single_block_row_attention(
        block_id,
        to_start_block_id,
        to_end_block_id,
        num_rand_blocks,
        window_block_left=1,
        window_block_right=1,
        global_block_left=1,
        global_block_right=1,
    ):
        """
        For a single row block get random row attention.

        Args:
            block_id: int. block id of row.
            to_start_block_id: int. random attention column start id.
            to_end_block_id: int. random attention column end id.
            num_rand_blocks: int. number of random blocks to be selected.
            window_block_left: int. number of blocks of window to left of a block.
            window_block_right: int. number of blocks of window to right of a block.
            global_block_left: int. Number of blocks globally used to the left.
            global_block_right: int. Number of blocks globally used to the right.

        Returns:
            row containing the random attention vector of size num_rand_blocks.
        """
        # list of to_blocks from which to choose random attention
        to_block_list = np.arange(to_start_block_id, to_end_block_id, dtype=np.int32)
        # permute the blocks
        perm_block = np.random.permutation(to_block_list)

        # illegal blocks for the current block id, using window
        illegal_blocks = list(range(block_id - window_block_left, block_id + window_block_right + 1))

        # Add blocks at the start and at the end
        illegal_blocks.extend(list(range(global_block_left)))
        illegal_blocks.extend(list(range(to_end_block_id - global_block_right, to_end_block_id)))

        # The second from_block cannot choose random attention on second last to_block
        if block_id == 1:
            illegal_blocks.append(to_end_block_id - 2)

        # The second last from_block cannot choose random attention on second to_block
        if block_id == to_end_block_id - 2:
            illegal_blocks.append(1)

        selected_random_blocks = []

        for i in range(to_end_block_id - to_start_block_id):
            if perm_block[i] not in illegal_blocks:
                selected_random_blocks.append(perm_block[i])
            if len(selected_random_blocks) == num_rand_blocks:
                break
        return np.array(selected_random_blocks, dtype=np.int32)


class BigBirdPegasusEncoderAttention(nn.Module):
    def __init__(self, config, seed=None):
        super().__init__()
        self.config = config
        self.seed = seed

        self.attention_type = config.attention_type

        if self.attention_type == "original_full":
            self.self = BigBirdPegasusSelfAttention(config)
        elif self.attention_type == "block_sparse":
            self.self = BigBirdPegasusBlockSparseAttention(config, seed)
        else:
            raise ValueError(
                f"attention_type can either be original_full or block_sparse, but is {self.config.attention_type}"
            )

        self.output = nn.Linear(config.hidden_size, config.hidden_size, bias=config.use_bias)

    def set_attention_type(self, value: str):
        if value not in ["original_full", "block_sparse"]:
            raise ValueError(
                f"attention_type can only be set to either 'original_full' or 'block_sparse', but is {value}"
            )
        # attention type is already correctly set
        if value == self.attention_type:
            return

        if value == "original_full":
            # copy all weights to new full attention class
            attn_weights = BigBirdPegasusSelfAttention(self.config)
        else:
            # copy all weights to new sparse attention class
            attn_weights = BigBirdPegasusBlockSparseAttention(self.config, self.seed)

        attn_weights.query = self.self.query
        attn_weights.value = self.self.value
        attn_weights.key = self.self.key
        self.self = attn_weights
        self.attention_type = value

        if not self.training:
            self.self.eval()

    def forward(
        self,
        hidden_states,
        attention_mask=None,
        band_mask=None,
        from_mask=None,
        to_mask=None,
        from_blocked_mask=None,
        to_blocked_mask=None,
        **kwargs: Unpack[TransformersKwargs],
    ):
        if self.attention_type == "original_full":
            context_layer, attention_probs = self.self(
                hidden_states,
                attention_mask,
                **kwargs,
            )
        else:
            context_layer, attention_probs = self.self(
                hidden_states,
                band_mask,
                from_mask,
                to_mask,
                from_blocked_mask,
                to_blocked_mask,
                **kwargs,
            )

        attention_output = self.output(context_layer)
        return attention_output, attention_probs


def eager_attention_forward(
    module: nn.Module,
    query: torch.Tensor,
    key: torch.Tensor,
    value: torch.Tensor,
    attention_mask: torch.Tensor | None,
    scaling: float | None = None,
    dropout: float = 0.0,
    **kwargs: Unpack[TransformersKwargs],
):
    if scaling is None:
        scaling = query.size(-1) ** -0.5

    # Take the dot product between "query" and "key" to get the raw attention scores.
    attn_weights = torch.matmul(query, key.transpose(2, 3)) * scaling

    if attention_mask is not None:
        attn_weights = attn_weights + attention_mask

    attn_weights = nn.functional.softmax(attn_weights, dim=-1)
    attn_weights = nn.functional.dropout(attn_weights, p=dropout, training=module.training)

    attn_output = torch.matmul(attn_weights.to(value.dtype), value)
    attn_output = attn_output.transpose(1, 2).contiguous()

    return attn_output, attn_weights


# Copied from transformers.models.bart.modeling_bart.BartAttention with BartConfig->BigBirdPegasusConfig, Bart->BigBirdPegasusDecoder
class BigBirdPegasusDecoderAttention(nn.Module):
    """Multi-headed attention from 'Attention Is All You Need' paper"""

    def __init__(
        self,
        embed_dim: int,
        num_heads: int,
        dropout: float = 0.0,
        is_decoder: bool = False,
        bias: bool = True,
        is_causal: bool = False,
        config: BigBirdPegasusConfig | None = None,
        layer_idx: int | None = None,
    ):
        super().__init__()
        self.embed_dim = embed_dim
        self.num_heads = num_heads
        self.dropout = dropout
        self.head_dim = embed_dim // num_heads
        self.config = config

        if (self.head_dim * num_heads) != self.embed_dim:
            raise ValueError(
                f"embed_dim must be divisible by num_heads (got `embed_dim`: {self.embed_dim}"
                f" and `num_heads`: {num_heads})."
            )
        self.scaling = self.head_dim**-0.5
        self.is_decoder = is_decoder
        self.is_causal = is_causal
        self.layer_idx = layer_idx
        if layer_idx is None and self.is_decoder:
            logger.warning_once(
                f"Instantiating a decoder {self.__class__.__name__} without passing `layer_idx` is not recommended and "
                "will lead to errors during the forward call, if caching is used. Please make sure to provide a `layer_idx` "
                "when creating this class."
            )

        self.k_proj = nn.Linear(embed_dim, embed_dim, bias=bias)
        self.v_proj = nn.Linear(embed_dim, embed_dim, bias=bias)
        self.q_proj = nn.Linear(embed_dim, embed_dim, bias=bias)
        self.out_proj = nn.Linear(embed_dim, embed_dim, bias=bias)

    def forward(
        self,
        hidden_states: torch.Tensor,
        key_value_states: torch.Tensor | None = None,
        past_key_values: Cache | None = None,
        attention_mask: torch.Tensor | None = None,
        # TODO: we need a refactor so that the different attention modules can get their specific kwargs
        # ATM, we have mixed things encoder, decoder, and encoder-decoder attn
        **kwargs: Unpack[FlashAttentionKwargs],
    ) -> tuple[torch.Tensor, torch.Tensor | None]:
        """Input shape: Batch x Time x Channel"""

        # if key_value_states are provided this layer is used as a cross-attention layer
        # for the decoder
        is_cross_attention = key_value_states is not None

        # determine input shapes
        bsz, tgt_len = hidden_states.shape[:-1]
        src_len = key_value_states.shape[1] if is_cross_attention else tgt_len

        q_input_shape = (bsz, tgt_len, -1, self.head_dim)
        kv_input_shape = (bsz, src_len, -1, self.head_dim)

        # get query proj
        query_states = self.q_proj(hidden_states).view(*q_input_shape).transpose(1, 2)

        is_updated = False
        if past_key_values is not None:
            if isinstance(past_key_values, EncoderDecoderCache):
                is_updated = past_key_values.is_updated.get(self.layer_idx)
                if is_cross_attention:
                    # after the first generated id, we can subsequently re-use all key/value_states from cache
                    curr_past_key_values = past_key_values.cross_attention_cache
                else:
                    curr_past_key_values = past_key_values.self_attention_cache
            else:
                curr_past_key_values = past_key_values

        current_states = key_value_states if is_cross_attention else hidden_states
        if is_cross_attention and past_key_values is not None and is_updated:
            # reuse k,v, cross_attentions
            key_states = curr_past_key_values.layers[self.layer_idx].keys
            value_states = curr_past_key_values.layers[self.layer_idx].values
        else:
            key_states = self.k_proj(current_states)
            value_states = self.v_proj(current_states)
            key_states = key_states.view(*kv_input_shape).transpose(1, 2)
            value_states = value_states.view(*kv_input_shape).transpose(1, 2)

            if past_key_values is not None:
                key_states, value_states = curr_past_key_values.update(key_states, value_states, self.layer_idx)
                # set flag that curr layer for cross-attn is already updated so we can re-use in subsequent calls
                if is_cross_attention and isinstance(past_key_values, EncoderDecoderCache):
                    past_key_values.is_updated[self.layer_idx] = True

        attention_interface: Callable = ALL_ATTENTION_FUNCTIONS.get_interface(
            self.config._attn_implementation, eager_attention_forward
        )

        attn_output, attn_weights = attention_interface(
            self,
            query_states,
            key_states,
            value_states,
            attention_mask,
            dropout=0.0 if not self.training else self.dropout,
            scaling=self.scaling,
            **kwargs,
        )

        attn_output = attn_output.reshape(bsz, tgt_len, -1).contiguous()
        attn_output = self.out_proj(attn_output)

        return attn_output, attn_weights


class BigBirdPegasusEncoderLayer(GradientCheckpointingLayer):
    def __init__(self, config: BigBirdPegasusConfig, seed=None):
        super().__init__()
        self.attention_type = config.attention_type
        self.embed_dim = config.d_model
        self.self_attn = BigBirdPegasusEncoderAttention(config, seed=seed)
        self.self_attn_layer_norm = nn.LayerNorm(self.embed_dim)
        self.dropout = config.dropout
        self.activation_fn = ACT2FN[config.activation_function]
        self.activation_dropout = config.activation_dropout
        self.fc1 = nn.Linear(self.embed_dim, config.encoder_ffn_dim)
        self.fc2 = nn.Linear(config.encoder_ffn_dim, self.embed_dim)
        self.final_layer_norm = nn.LayerNorm(self.embed_dim)

    def forward(
        self,
        hidden_states: torch.Tensor,
        attention_mask: torch.Tensor,
        band_mask=None,
        from_mask=None,
        to_mask=None,
        from_blocked_mask=None,
        to_blocked_mask=None,
        **kwargs: Unpack[TransformersKwargs],
    ) -> torch.Tensor:
        residual = hidden_states
        hidden_states = self.self_attn_layer_norm(hidden_states)

        hidden_states, _ = self.self_attn(
            hidden_states,
            attention_mask=attention_mask,
            band_mask=band_mask,
            from_mask=from_mask,
            to_mask=to_mask,
            from_blocked_mask=from_blocked_mask,
            to_blocked_mask=to_blocked_mask,
            **kwargs,
        )

        hidden_states = nn.functional.dropout(hidden_states, p=self.dropout, training=self.training)
        hidden_states = residual + hidden_states

        residual = hidden_states
        hidden_states = self.final_layer_norm(hidden_states)
        hidden_states = self.activation_fn(self.fc1(hidden_states))

        hidden_states = self.fc2(hidden_states)
        hidden_states = nn.functional.dropout(hidden_states, p=self.dropout, training=self.training)
        hidden_states = residual + hidden_states

        if hidden_states.dtype == torch.float16 and not torch.isfinite(hidden_states).all():
            clamp_value = torch.finfo(hidden_states.dtype).max - 1000
            hidden_states = torch.clamp(hidden_states, min=-clamp_value, max=clamp_value)

        return hidden_states

    def set_attention_type(self, value: str):
        if value not in ["original_full", "block_sparse"]:
            raise ValueError(
                f"attention_type can only be set to either 'original_full' or 'block_sparse', but is {value}"
            )
        # attention type is already correctly set
        if value == self.attention_type:
            return
        self.attention_type = value
        self.self_attn.set_attention_type(value)


class BigBirdPegasusDecoderLayer(GradientCheckpointingLayer):
    def __init__(self, config: BigBirdPegasusConfig, layer_idx: int | None = None):
        super().__init__()
        self.embed_dim = config.d_model
        self.self_attn = BigBirdPegasusDecoderAttention(
            embed_dim=self.embed_dim,
            num_heads=config.decoder_attention_heads,
            dropout=config.attention_dropout,
            is_decoder=True,
            bias=config.use_bias,
            config=config,
            layer_idx=layer_idx,
        )
        self.dropout = config.dropout
        self.activation_fn = ACT2FN[config.activation_function]
        self.activation_dropout = config.activation_dropout

        self.self_attn_layer_norm = nn.LayerNorm(self.embed_dim)
        self.encoder_attn = BigBirdPegasusDecoderAttention(
            self.embed_dim,
            config.decoder_attention_heads,
            dropout=config.attention_dropout,
            is_decoder=True,
            bias=config.use_bias,
            config=config,
            layer_idx=layer_idx,
        )
        self.encoder_attn_layer_norm = nn.LayerNorm(self.embed_dim)
        self.fc1 = nn.Linear(self.embed_dim, config.decoder_ffn_dim)
        self.fc2 = nn.Linear(config.decoder_ffn_dim, self.embed_dim)
        self.final_layer_norm = nn.LayerNorm(self.embed_dim)

    # Copied from transformers.models.mbart.modeling_mbart.MBartDecoderLayer.forward
    def forward(
        self,
        hidden_states: torch.Tensor,
        attention_mask: torch.Tensor | None = None,
        encoder_hidden_states: torch.Tensor | None = None,
        encoder_attention_mask: torch.Tensor | None = None,
        past_key_values: Cache | None = None,
        use_cache: bool | None = True,
        **kwargs: Unpack[TransformersKwargs],
    ) -> torch.Tensor:
        """
        Args:
            hidden_states (`torch.FloatTensor`): input to the layer of shape `(batch, seq_len, embed_dim)`
            attention_mask (`torch.FloatTensor`): attention mask of size
                `(batch, 1, tgt_len, src_len)` where padding elements are indicated by very large negative values.
            encoder_hidden_states (`torch.FloatTensor`):
                cross attention input to the layer of shape `(batch, seq_len, embed_dim)`
            encoder_attention_mask (`torch.FloatTensor`): encoder attention mask of size
                `(batch, 1, tgt_len, src_len)` where padding elements are indicated by very large negative values.
            past_key_values (`Cache`): cached past key and value projection states
        """
        residual = hidden_states
        hidden_states = self.self_attn_layer_norm(hidden_states)

        # Self Attention
        hidden_states, _ = self.self_attn(
            hidden_states=hidden_states,
            past_key_values=past_key_values,
            attention_mask=attention_mask,
            **kwargs,
        )
        hidden_states = nn.functional.dropout(hidden_states, p=self.dropout, training=self.training)
        hidden_states = residual + hidden_states

        # Cross-Attention Block
        if encoder_hidden_states is not None:
            residual = hidden_states
            hidden_states = self.encoder_attn_layer_norm(hidden_states)

            hidden_states, _ = self.encoder_attn(
                hidden_states=hidden_states,
                key_value_states=encoder_hidden_states,
                attention_mask=encoder_attention_mask,
                past_key_values=past_key_values,
                **kwargs,
            )
            hidden_states = nn.functional.dropout(hidden_states, p=self.dropout, training=self.training)
            hidden_states = residual + hidden_states

        # Fully Connected
        residual = hidden_states
        hidden_states = self.final_layer_norm(hidden_states)
        hidden_states = self.activation_fn(self.fc1(hidden_states))
        hidden_states = nn.functional.dropout(hidden_states, p=self.activation_dropout, training=self.training)
        hidden_states = self.fc2(hidden_states)
        hidden_states = nn.functional.dropout(hidden_states, p=self.dropout, training=self.training)
        hidden_states = residual + hidden_states

        return hidden_states


# Copied from transformers.models.bart.modeling_bart.BartClassificationHead with Bart->BigBirdPegasus
class BigBirdPegasusClassificationHead(nn.Module):
    """Head for sentence-level classification tasks."""

    def __init__(
        self,
        input_dim: int,
        inner_dim: int,
        num_classes: int,
        pooler_dropout: float,
    ):
        super().__init__()
        self.dense = nn.Linear(input_dim, inner_dim)
        self.dropout = nn.Dropout(p=pooler_dropout)
        self.out_proj = nn.Linear(inner_dim, num_classes)

    def forward(self, hidden_states: torch.Tensor) -> torch.Tensor:
        hidden_states = self.dropout(hidden_states)
        hidden_states = self.dense(hidden_states)
        hidden_states = torch.tanh(hidden_states)
        hidden_states = self.dropout(hidden_states)
        hidden_states = self.out_proj(hidden_states)
        return hidden_states


@auto_docstring
class BigBirdPegasusPreTrainedModel(PreTrainedModel):
    config: BigBirdPegasusConfig
    base_model_prefix = "model"
    supports_gradient_checkpointing = True
    _no_split_modules = ["BigBirdPegasusEncoderLayer", "BigBirdPegasusDecoderLayer"]
    _skip_keys_device_placement = "past_key_values"
    _can_compile_fullgraph = True

    def _init_weights(self, module):
        super()._init_weights(module)
        if isinstance(module, BigBirdPegasusForConditionalGeneration):
            init.zeros_(module.final_logits_bias)

    @property
    def dummy_inputs(self):
        pad_token = self.config.pad_token_id
        input_ids = torch.tensor([[0, 6, 10, 4, 2], [0, 8, 12, 2, pad_token]], device=self.device)
        dummy_inputs = {
            "attention_mask": input_ids.ne(pad_token),
            "input_ids": input_ids,
        }
        return dummy_inputs


class BigBirdPegasusEncoder(BigBirdPegasusPreTrainedModel):
    """
    Transformer encoder consisting of *config.encoder_layers* self attention layers. Each layer is a
    [`BigBirdPegasusEncoderLayer`].

    Args:
        config: BigBirdPegasusConfig
        embed_tokens (nn.Embedding): output embedding
    """

    _can_record_outputs = {
        "hidden_states": BigBirdPegasusEncoderLayer,
        "attentions": BigBirdPegasusEncoderAttention,
    }

    def __init__(self, config: BigBirdPegasusConfig):
        super().__init__(config)

        self.attention_type = config.attention_type
        self.block_size = config.block_size

        self.dropout = config.dropout
        self.layerdrop = config.encoder_layerdrop

        embed_dim = config.d_model
        self.padding_idx = config.pad_token_id
        self.max_source_positions = config.max_position_embeddings
        embed_scale = math.sqrt(embed_dim) if config.scale_embedding else 1.0

        self.embed_tokens = BigBirdPegasusScaledWordEmbedding(
            config.vocab_size, embed_dim, self.padding_idx, embed_scale=embed_scale
        )

        self.embed_positions = BigBirdPegasusLearnedPositionalEmbedding(
            config.max_position_embeddings,
            embed_dim,
        )
        self.layers = nn.ModuleList([BigBirdPegasusEncoderLayer(config, seed=i) for i in range(config.encoder_layers)])
        self.layernorm_embedding = nn.LayerNorm(embed_dim)

        self.gradient_checkpointing = False
        # Initialize weights and apply final processing
        self.post_init()

    @merge_with_config_defaults
    @capture_outputs
    @auto_docstring
    def forward(
        self,
        input_ids: torch.Tensor | None = None,
        attention_mask: torch.Tensor | None = None,
        inputs_embeds: torch.Tensor | None = None,
        **kwargs: Unpack[TransformersKwargs],
    ) -> BaseModelOutput:
        if (input_ids is None) ^ (inputs_embeds is not None):
            raise ValueError("You must specify exactly one of input_ids or inputs_embeds")

        if inputs_embeds is None:
            inputs_embeds = self.embed_tokens(input_ids)

        input_shape = inputs_embeds.size()[:-1]
        embed_pos = self.embed_positions(input_shape)

        hidden_states = inputs_embeds + embed_pos
        hidden_states = nn.functional.dropout(hidden_states, p=self.dropout, training=self.training)

        if attention_mask is None:
            attention_mask = torch.ones(input_shape, device=hidden_states.device)
        attention_mask = attention_mask.long()

        # in order to use block_sparse attention, sequence_length has to be at least
        # bigger than all global attentions: 2 * block_size
        # + sliding tokens: 3 * block_size
        # + random tokens: 2 * num_random_blocks * block_size
        max_tokens_to_attend = (5 + 2 * self.config.num_random_blocks) * self.config.block_size
        if self.attention_type == "block_sparse" and input_shape[1] <= max_tokens_to_attend:
            # change attention_type from block_sparse to original_full
            sequence_length = input_shape[1]
            logger.warning(
                "Attention type 'block_sparse' is not possible if sequence_length: "
                f"{sequence_length} <= num global tokens: 2 * config.block_size "
                "+ min. num sliding tokens: 3 * config.block_size "
                "+ config.num_random_blocks * config.block_size "
                "+ additional buffer: config.num_random_blocks * config.block_size "
                f"= {max_tokens_to_attend} with config.block_size "
                f"= {self.config.block_size}, config.num_random_blocks "
                f"= {self.config.num_random_blocks}. "
                "Changing attention type to 'original_full'..."
            )
            self.set_attention_type("original_full")

        if self.attention_type == "block_sparse":
            padding_len, hidden_states, attention_mask = self._pad_to_block_size(hidden_states, attention_mask)
        else:
            padding_len = 0

        # expand attention_mask
        if self.attention_type == "original_full":
            # [bsz, seq_len] -> [bsz, 1, tgt_seq_len, src_seq_len]
            attention_mask = create_bidirectional_mask(
                config=self.config,
                inputs_embeds=inputs_embeds,
                attention_mask=attention_mask,
            )
            blocked_encoder_mask = band_mask = from_mask = to_mask = None
        elif self.attention_type == "block_sparse":
            blocked_encoder_mask, band_mask, from_mask, to_mask = self.create_masks_for_block_sparse_attn(
                attention_mask, self.block_size
            )
            attention_mask = None
        else:
            raise ValueError(
                f"attention_type can either be original_full or block_sparse, but is {self.attention_type}"
            )

        for idx, encoder_layer in enumerate(self.layers):
            # add LayerDrop (see https://huggingface.co/papers/1909.11556 for description)
            to_drop = False
            if self.training:
                dropout_probability = torch.rand([])
                if dropout_probability < self.layerdrop:  # skip the layer
                    to_drop = True

            if not to_drop:
                hidden_states = encoder_layer(
                    hidden_states,
                    attention_mask,
                    band_mask=band_mask,
                    from_mask=from_mask,
                    to_mask=to_mask,
                    from_blocked_mask=blocked_encoder_mask,
                    to_blocked_mask=blocked_encoder_mask,
                    **kwargs,
                )

        hidden_states = self.layernorm_embedding(hidden_states)

        if padding_len > 0:
            # unpad `sequence_output` because the calling function is expecting a length == input_ids.size(1)
            hidden_states = hidden_states[:, :-padding_len]

        return BaseModelOutput(
            last_hidden_state=hidden_states,
        )

    def set_attention_type(self, value: str):
        if value not in ["original_full", "block_sparse"]:
            raise ValueError(
                f"attention_type can only be set to either 'original_full' or 'block_sparse', but is {value}"
            )
        # attention type is already correctly set
        if value == self.attention_type:
            return
        self.attention_type = value
        for layer in self.layers:
            layer.set_attention_type(value)

    @staticmethod  # Copied from transformers.models.big_bird.modeling_big_bird.BigBirdModel.create_masks_for_block_sparse_attn
    def create_masks_for_block_sparse_attn(attention_mask: torch.Tensor, block_size: int):
        batch_size, seq_length = attention_mask.size()
        if seq_length % block_size != 0:
            raise ValueError(
                f"Sequence length must be multiple of block size, but sequence length is {seq_length}, while block"
                f" size is {block_size}."
            )

        def create_band_mask_from_inputs(from_blocked_mask, to_blocked_mask):
            """
            Create 3D attention mask from a 2D tensor mask.

            Args:
                from_blocked_mask: 2D Tensor of shape [batch_size,
                from_seq_length//from_block_size, from_block_size].
                to_blocked_mask: int32 Tensor of shape [batch_size,
                to_seq_length//to_block_size, to_block_size].

            Returns:
                float Tensor of shape [batch_size, 1, from_seq_length//from_block_size-4, from_block_size,
                3*to_block_size].
            """
            exp_blocked_to_pad = torch.cat(
                [to_blocked_mask[:, 1:-3], to_blocked_mask[:, 2:-2], to_blocked_mask[:, 3:-1]], dim=2
            )
            band_mask = torch.einsum("blq,blk->blqk", from_blocked_mask[:, 2:-2], exp_blocked_to_pad)
            band_mask.unsqueeze_(1)
            return band_mask

        blocked_encoder_mask = attention_mask.view(batch_size, seq_length // block_size, block_size)
        band_mask = create_band_mask_from_inputs(blocked_encoder_mask, blocked_encoder_mask)

        from_mask = attention_mask.view(batch_size, 1, seq_length, 1)
        to_mask = attention_mask.view(batch_size, 1, 1, seq_length)

        return blocked_encoder_mask, band_mask, from_mask, to_mask

    def _pad_to_block_size(self, hidden_states: torch.Tensor, attention_mask: torch.Tensor):
        """A helper function to pad tokens and mask to work with implementation of BigBird block-sparse attention."""
        # padding
        block_size = self.config.block_size
        batch_size, seq_len = hidden_states.shape[:2]

        padding_len = (block_size - seq_len % block_size) % block_size
        if padding_len > 0:
            logger.warning_once(
                f"Input ids are automatically padded from {seq_len} to {seq_len + padding_len} to be a multiple of "
                f"`config.block_size`: {block_size}"
            )
            pad_id = self.config.pad_token_id
            device = hidden_states.device
            input_ids_padding = torch.ones((batch_size, padding_len), dtype=torch.long, device=device) * pad_id
            inputs_embeds_padding = self.embed_tokens(input_ids_padding)
            hidden_states = torch.cat([hidden_states, inputs_embeds_padding], dim=-2)

            attention_mask = nn.functional.pad(
                attention_mask, (0, padding_len), value=0
            )  # no attention on the padding tokens

        return padding_len, hidden_states, attention_mask


class BigBirdPegasusDecoder(BigBirdPegasusPreTrainedModel):
    """
    Transformer decoder consisting of *config.decoder_layers* layers. Each layer is a [`BigBirdPegasusDecoderLayer`]

    Args:
        config: BigBirdPegasusConfig
        embed_tokens (nn.Embedding): output embedding
    """

    _can_record_outputs = {
        "hidden_states": BigBirdPegasusDecoderLayer,
        "attentions": OutputRecorder(BigBirdPegasusDecoderAttention, index=1, layer_name="self_attn"),
        "cross_attentions": OutputRecorder(BigBirdPegasusDecoderAttention, index=1, layer_name="encoder_attn"),
    }

    def __init__(self, config: BigBirdPegasusConfig):
        super().__init__(config)
        self.dropout = config.dropout
        self.layerdrop = config.decoder_layerdrop
        self.padding_idx = config.pad_token_id
        self.max_target_positions = config.max_position_embeddings
        embed_scale = math.sqrt(config.d_model) if config.scale_embedding else 1.0

        self.embed_tokens = BigBirdPegasusScaledWordEmbedding(
            config.vocab_size, config.d_model, self.padding_idx, embed_scale=embed_scale
        )

        self.embed_positions = BigBirdPegasusLearnedPositionalEmbedding(
            config.max_position_embeddings,
            config.d_model,
        )
        self.layers = nn.ModuleList(
            [BigBirdPegasusDecoderLayer(config, layer_idx=i) for i in range(config.decoder_layers)]
        )
        self.layernorm_embedding = nn.LayerNorm(config.d_model)

        self.gradient_checkpointing = False
        # Initialize weights and apply final processing
        self.post_init()

    @merge_with_config_defaults
    @capture_outputs
    @auto_docstring
    def forward(
        self,
        input_ids: torch.LongTensor | None = None,
        attention_mask: torch.Tensor | None = None,
        encoder_hidden_states: torch.FloatTensor | None = None,
        encoder_attention_mask: torch.LongTensor | None = None,
        past_key_values: Cache | None = None,
        inputs_embeds: torch.FloatTensor | None = None,
        use_cache: bool | None = None,
        **kwargs: Unpack[TransformersKwargs],
    ) -> BaseModelOutputWithPastAndCrossAttentions:
        if (input_ids is None) ^ (inputs_embeds is not None):
            raise ValueError("You cannot specify both decoder_input_ids and decoder_inputs_embeds at the same time")

        if inputs_embeds is None:
            inputs_embeds = self.embed_tokens(input_ids)

        # initialize `past_key_values`
        if use_cache and past_key_values is None:
            past_key_values = (
                EncoderDecoderCache(DynamicCache(config=self.config), DynamicCache(config=self.config))
                if encoder_hidden_states is not None or self.config.is_encoder_decoder
                else DynamicCache(config=self.config)
            )

        batch_size, seq_length = inputs_embeds.size()[:-1]
        past_key_values_length = past_key_values.get_seq_length() if past_key_values is not None else 0
        position_ids = torch.arange(seq_length, device=inputs_embeds.device) + past_key_values_length

        if attention_mask is None and not is_torchdynamo_compiling():
            # required mask seq length can be calculated via length of past cache
            mask_seq_length = past_key_values_length + seq_length
            attention_mask = torch.ones(batch_size, mask_seq_length, device=inputs_embeds.device)

        self_attn_cache = (
            past_key_values.self_attention_cache
            if isinstance(past_key_values, EncoderDecoderCache)
            else past_key_values
        )

        attention_mask = create_causal_mask(
            config=self.config,
            inputs_embeds=inputs_embeds,
            attention_mask=attention_mask,
            past_key_values=self_attn_cache,
        )
        encoder_attention_mask = create_bidirectional_mask(
            config=self.config,
            inputs_embeds=inputs_embeds,
            attention_mask=encoder_attention_mask,
            encoder_hidden_states=encoder_hidden_states,
        )

        # embed positions
        positions = self.embed_positions(input, past_key_values_length, position_ids=position_ids)
        positions = positions.to(inputs_embeds.device)

        hidden_states = inputs_embeds + positions

        hidden_states = nn.functional.dropout(hidden_states, p=self.dropout, training=self.training)

        for idx, decoder_layer in enumerate(self.layers):
            # add LayerDrop (see https://huggingface.co/papers/1909.11556 for description)
            if self.training:
                dropout_probability = torch.rand([])
                if dropout_probability < self.layerdrop:
                    continue

            hidden_states = decoder_layer(
                hidden_states,
                attention_mask,
                encoder_hidden_states,  # as a positional argument for gradient checkpointing
                encoder_attention_mask=encoder_attention_mask,
                past_key_values=past_key_values,
                use_cache=use_cache,
                **kwargs,
            )

        hidden_states = self.layernorm_embedding(hidden_states)

        return BaseModelOutputWithPastAndCrossAttentions(
            last_hidden_state=hidden_states,
            past_key_values=past_key_values,
        )


@auto_docstring
class BigBirdPegasusModel(BigBirdPegasusPreTrainedModel):
    _tied_weights_keys = {
        "encoder.embed_tokens.weight": "shared.weight",
        "decoder.embed_tokens.weight": "shared.weight",
    }

    def __init__(self, config: BigBirdPegasusConfig):
        super().__init__(config)

        padding_idx, vocab_size = config.pad_token_id, config.vocab_size
        embed_scale = math.sqrt(config.d_model) if config.scale_embedding else 1.0
        self.shared = BigBirdPegasusScaledWordEmbedding(
            vocab_size, config.d_model, padding_idx, embed_scale=embed_scale
        )

        self.encoder = BigBirdPegasusEncoder(config)
        self.decoder = BigBirdPegasusDecoder(config)

        # Initialize weights and apply final processing
        self.post_init()

    def get_input_embeddings(self):
        return self.shared

    def set_input_embeddings(self, value):
        self.shared = value
        self.encoder.embed_tokens = self.shared
        self.decoder.embed_tokens = self.shared

    @can_return_tuple
    @auto_docstring
    def forward(
        self,
        input_ids: torch.LongTensor | None = None,
        attention_mask: torch.Tensor | None = None,
        decoder_input_ids: torch.LongTensor | None = None,
        decoder_attention_mask: torch.LongTensor | None = None,
        encoder_outputs: list[torch.FloatTensor] | None = None,
        past_key_values: Cache | None = None,
        inputs_embeds: torch.FloatTensor | None = None,
        decoder_inputs_embeds: torch.FloatTensor | None = None,
        use_cache: bool | None = None,
        **kwargs: Unpack[TransformersKwargs],
    ) -> tuple | Seq2SeqModelOutput:
        r"""
        decoder_input_ids (`torch.LongTensor` of shape `(batch_size, target_sequence_length)`, *optional*):
            Provide for translation and summarization training. By default, the model will create this tensor by
            shifting the `input_ids` to the right, following the paper.
        decoder_attention_mask (`torch.LongTensor` of shape `(batch_size, target_sequence_length)`, *optional*):
            Default behavior: generate a tensor that ignores pad tokens in `decoder_input_ids`. Causal mask will also
            be used by default.

            If you want to change padding behavior, you should read
            [`modeling_bigbird_pegasus._prepare_decoder_attention_mask`] and modify to your needs. See diagram 1 in
            [the paper](https://huggingface.co/papers/1910.13461) for more information on the default strategy.
        """
        # different to other models, BigBirdPegasus automatically creates decoder_input_ids from
        # input_ids if no decoder_input_ids are provided
        if decoder_input_ids is None and decoder_inputs_embeds is None:
            if input_ids is None:
                raise ValueError(
                    "If no `decoder_input_ids` or `decoder_inputs_embeds` are "
                    "passed, `input_ids` cannot be `None`. Please pass either "
                    "`input_ids` or `decoder_input_ids` or `decoder_inputs_embeds`."
                )

            decoder_input_ids = shift_tokens_right(
                input_ids, self.config.pad_token_id, self.config.decoder_start_token_id
            )

        if encoder_outputs is None:
            encoder_outputs: BaseModelOutput = self.encoder(
                input_ids=input_ids,
                attention_mask=attention_mask,
                inputs_embeds=inputs_embeds,
                **kwargs,
            )
        elif not isinstance(encoder_outputs, BaseModelOutput):
            encoder_outputs = BaseModelOutput(
                last_hidden_state=encoder_outputs[0],
                hidden_states=encoder_outputs[1] if len(encoder_outputs) > 1 else None,
                attentions=encoder_outputs[2] if len(encoder_outputs) > 2 else None,
            )

        decoder_outputs: BaseModelOutputWithPastAndCrossAttentions = self.decoder(
            input_ids=decoder_input_ids,
            attention_mask=decoder_attention_mask,
            encoder_hidden_states=encoder_outputs[0],
            encoder_attention_mask=attention_mask,
            past_key_values=past_key_values,
            inputs_embeds=decoder_inputs_embeds,
            use_cache=use_cache,
            **kwargs,
        )

        return Seq2SeqModelOutput(
            last_hidden_state=decoder_outputs.last_hidden_state,
            past_key_values=decoder_outputs.past_key_values,
            decoder_hidden_states=decoder_outputs.hidden_states,
            decoder_attentions=decoder_outputs.attentions,
            cross_attentions=decoder_outputs.cross_attentions,
            encoder_last_hidden_state=encoder_outputs.last_hidden_state,
            encoder_hidden_states=encoder_outputs.hidden_states,
            encoder_attentions=encoder_outputs.attentions,
        )


@auto_docstring(
    custom_intro="""
    The BigBirdPegasus Model with a language modeling head. Can be used for summarization.
    """
)
class BigBirdPegasusForConditionalGeneration(BigBirdPegasusPreTrainedModel, GenerationMixin):
    base_model_prefix = "model"
    _tied_weights_keys = {
        "lm_head.weight": "model.shared.weight",
    }
    _keys_to_ignore_on_load_missing = ["final_logits_bias"]

    # Copied from transformers.models.bart.modeling_bart.BartForConditionalGeneration.__init__ with Bart->BigBirdPegasus, BART->BIGBIRD_PEGASUS
    def __init__(self, config: BigBirdPegasusConfig):
        super().__init__(config)
        self.model = BigBirdPegasusModel(config)
        self.register_buffer("final_logits_bias", torch.zeros((1, self.model.shared.num_embeddings)))
        self.lm_head = nn.Linear(config.d_model, self.model.shared.num_embeddings, bias=False)

        # Initialize weights and apply final processing
        self.post_init()

    # Copied from transformers.models.bart.modeling_bart.BartForConditionalGeneration.resize_token_embeddings with Bart->BigBirdPegasus, BART->BIGBIRD_PEGASUS
    def resize_token_embeddings(
        self, new_num_tokens: int, pad_to_multiple_of: int | None = None, mean_resizing: bool = True
    ) -> nn.Embedding:
        new_embeddings = super().resize_token_embeddings(new_num_tokens, pad_to_multiple_of, mean_resizing)
        self._resize_final_logits_bias(new_embeddings.weight.shape[0])
        return new_embeddings

    # Copied from transformers.models.bart.modeling_bart.BartForConditionalGeneration._resize_final_logits_bias with Bart->BigBirdPegasus, BART->BIGBIRD_PEGASUS
    def _resize_final_logits_bias(self, new_num_tokens: int) -> None:
        old_num_tokens = self.final_logits_bias.shape[-1]
        if new_num_tokens <= old_num_tokens:
            new_bias = self.final_logits_bias[:, :new_num_tokens]
        else:
            extra_bias = torch.zeros((1, new_num_tokens - old_num_tokens), device=self.final_logits_bias.device)
            new_bias = torch.cat([self.final_logits_bias, extra_bias], dim=1)
        self.register_buffer("final_logits_bias", new_bias)

    @can_return_tuple
    @auto_docstring
    def forward(
        self,
        input_ids: torch.LongTensor | None = None,
        attention_mask: torch.Tensor | None = None,
        decoder_input_ids: torch.LongTensor | None = None,
        decoder_attention_mask: torch.LongTensor | None = None,
        encoder_outputs: list[torch.FloatTensor] | None = None,
        past_key_values: Cache | None = None,
        inputs_embeds: torch.FloatTensor | None = None,
        decoder_inputs_embeds: torch.FloatTensor | None = None,
        labels: torch.LongTensor | None = None,
        use_cache: bool | None = None,
        **kwargs: Unpack[TransformersKwargs],
    ) -> tuple | Seq2SeqLMOutput:
        r"""
        decoder_input_ids (`torch.LongTensor` of shape `(batch_size, target_sequence_length)`, *optional*):
            Provide for translation and summarization training. By default, the model will create this tensor by
            shifting the `input_ids` to the right, following the paper.
        decoder_attention_mask (`torch.LongTensor` of shape `(batch_size, target_sequence_length)`, *optional*):
            Default behavior: generate a tensor that ignores pad tokens in `decoder_input_ids`. Causal mask will also
            be used by default.

            If you want to change padding behavior, you should read
            [`modeling_bigbird_pegasus._prepare_decoder_attention_mask`] and modify to your needs. See diagram 1 in
            [the paper](https://huggingface.co/papers/1910.13461) for more information on the default strategy.
        labels (`torch.LongTensor` of shape `(batch_size, sequence_length)`, *optional*):
            Labels for computing the masked language modeling loss. Indices should either be in `[0, ...,
            config.vocab_size]` or -100 (see `input_ids` docstring). Tokens with indices set to `-100` are ignored
            (masked), the loss is only computed for the tokens with labels in `[0, ..., config.vocab_size]`.

        Example summarization:

        ```python
        >>> from transformers import AutoTokenizer, BigBirdPegasusForConditionalGeneration

        >>> model = BigBirdPegasusForConditionalGeneration.from_pretrained("google/bigbird-pegasus-large-arxiv")
        >>> tokenizer = AutoTokenizer.from_pretrained("google/bigbird-pegasus-large-arxiv")

        >>> ARTICLE_TO_SUMMARIZE = (
        ...     "The dominant sequence transduction models are based on complex recurrent or convolutional neural "
        ...     "networks in an encoder-decoder configuration. The best performing models also connect the encoder "
        ...     "and decoder through an attention mechanism. We propose a new simple network architecture, the Transformer, "
        ...     "based solely on attention mechanisms, dispensing with recurrence and convolutions entirely. "
        ...     "Experiments on two machine translation tasks show these models to be superior in quality "
        ...     "while being more parallelizable and requiring significantly less time to train."
        ... )
        >>> inputs = tokenizer([ARTICLE_TO_SUMMARIZE], max_length=4096, return_tensors="pt", truncation=True)

        >>> # Generate Summary
        >>> summary_ids = model.generate(inputs["input_ids"], num_beams=4, max_length=15)
        >>> tokenizer.batch_decode(summary_ids, skip_special_tokens=True, clean_up_tokenization_spaces=False)[0]
        'dominant sequence models are based on recurrent or convolutional neural networks .'
        ```
        """
        if labels is not None:
            if use_cache:
                logger.warning("The `use_cache` argument is changed to `False` since `labels` is provided.")
            use_cache = False
            if decoder_input_ids is None and decoder_inputs_embeds is None:
                decoder_input_ids = shift_tokens_right(
                    labels, self.config.pad_token_id, self.config.decoder_start_token_id
                )

        outputs: Seq2SeqModelOutput = self.model(
            input_ids,
            attention_mask=attention_mask,
            decoder_input_ids=decoder_input_ids,
            encoder_outputs=encoder_outputs,
            decoder_attention_mask=decoder_attention_mask,
            past_key_values=past_key_values,
            inputs_embeds=inputs_embeds,
            decoder_inputs_embeds=decoder_inputs_embeds,
            use_cache=use_cache,
            **kwargs,
        )

        lm_logits = self.lm_head(outputs[0])
        lm_logits = lm_logits + self.final_logits_bias.to(lm_logits.device)

        masked_lm_loss = None
        if labels is not None:
            labels = labels.to(lm_logits.device)
            loss_fct = CrossEntropyLoss()
            masked_lm_loss = loss_fct(lm_logits.view(-1, self.config.vocab_size), labels.view(-1))

        return Seq2SeqLMOutput(
            loss=masked_lm_loss,
            logits=lm_logits,
            past_key_values=outputs.past_key_values,
            decoder_hidden_states=outputs.decoder_hidden_states,
            decoder_attentions=outputs.decoder_attentions,
            cross_attentions=outputs.cross_attentions,
            encoder_last_hidden_state=outputs.encoder_last_hidden_state,
            encoder_hidden_states=outputs.encoder_hidden_states,
            encoder_attentions=outputs.encoder_attentions,
        )

    # Copied from transformers.models.bart.modeling_bart.BartForConditionalGeneration.prepare_decoder_input_ids_from_labels with Bart->BigBirdPegasus, BART->BIGBIRD_PEGASUS
    def prepare_decoder_input_ids_from_labels(self, labels: torch.Tensor):
        return shift_tokens_right(labels, self.config.pad_token_id, self.config.decoder_start_token_id)


@auto_docstring(
    custom_intro="""
    BigBirdPegasus model with a sequence classification/head on top (a linear layer on top of the pooled output) e.g.
    for GLUE tasks.
    """
)
class BigBirdPegasusForSequenceClassification(BigBirdPegasusPreTrainedModel):
    def __init__(self, config: BigBirdPegasusConfig, **kwargs):
        super().__init__(config, **kwargs)
        self.model = BigBirdPegasusModel(config)
        self.classification_head = BigBirdPegasusClassificationHead(
            config.d_model,
            config.d_model,
            config.num_labels,
            config.classifier_dropout,
        )

        # Initialize weights and apply final processing
        self.post_init()

    @can_return_tuple
    @auto_docstring
    def forward(
        self,
        input_ids: torch.LongTensor | None = None,
        attention_mask: torch.Tensor | None = None,
        decoder_input_ids: torch.LongTensor | None = None,
        decoder_attention_mask: torch.LongTensor | None = None,
        encoder_outputs: list[torch.FloatTensor] | None = None,
        inputs_embeds: torch.FloatTensor | None = None,
        decoder_inputs_embeds: torch.FloatTensor | None = None,
        labels: torch.LongTensor | None = None,
        use_cache: bool | None = None,
        **kwargs: Unpack[TransformersKwargs],
    ) -> tuple | Seq2SeqSequenceClassifierOutput:
        r"""
        decoder_input_ids (`torch.LongTensor` of shape `(batch_size, target_sequence_length)`, *optional*):
            Provide for translation and summarization training. By default, the model will create this tensor by
            shifting the `input_ids` to the right, following the paper.
        decoder_attention_mask (`torch.LongTensor` of shape `(batch_size, target_sequence_length)`, *optional*):
            Default behavior: generate a tensor that ignores pad tokens in `decoder_input_ids`. Causal mask will also
            be used by default.

            If you want to change padding behavior, you should read
            [`modeling_bigbird_pegasus._prepare_decoder_attention_mask`] and modify to your needs. See diagram 1 in
            [the paper](https://huggingface.co/papers/1910.13461) for more information on the default strategy.
        labels (`torch.LongTensor` of shape `(batch_size,)`, *optional*):
            Labels for computing the sequence classification/regression loss. Indices should be in `[0, ...,
            config.num_labels - 1]`. If `config.num_labels > 1` a classification loss is computed (Cross-Entropy).
        """
        if labels is not None:
            use_cache = False

        if input_ids is None and inputs_embeds is not None:
            raise NotImplementedError(
                f"Passing input embeddings is currently not supported for {self.__class__.__name__}"
            )

        outputs: Seq2SeqModelOutput = self.model(
            input_ids,
            attention_mask=attention_mask,
            decoder_input_ids=decoder_input_ids,
            decoder_attention_mask=decoder_attention_mask,
            encoder_outputs=encoder_outputs,
            inputs_embeds=inputs_embeds,
            decoder_inputs_embeds=decoder_inputs_embeds,
            use_cache=use_cache,
            **kwargs,
        )
        hidden_states = outputs[0]  # last hidden state

        eos_mask = input_ids.eq(self.config.eos_token_id).to(hidden_states.device)

        torch_compilable_check(
            torch.unique_consecutive(eos_mask.sum(1)).numel() == 1,
            "All examples must have the same number of <eos> tokens.",
        )
        sentence_representation = hidden_states[eos_mask, :].view(hidden_states.size(0), -1, hidden_states.size(-1))[
            :, -1, :
        ]
        logits = self.classification_head(sentence_representation)

        loss = None
        if labels is not None:
            labels = labels.to(logits.device)
            if self.config.problem_type is None:
                if self.config.num_labels == 1:
                    self.config.problem_type = "regression"
                elif self.config.num_labels > 1 and (labels.dtype == torch.long or labels.dtype == torch.int):
                    self.config.problem_type = "single_label_classification"
                else:
                    self.config.problem_type = "multi_label_classification"

            if self.config.problem_type == "regression":
                loss_fct = MSELoss()
                if self.config.num_labels == 1:
                    loss = loss_fct(logits.squeeze(), labels.squeeze())
                else:
                    loss = loss_fct(logits, labels)
            elif self.config.problem_type == "single_label_classification":
                loss_fct = CrossEntropyLoss()
                loss = loss_fct(logits.view(-1, self.config.num_labels), labels.view(-1))
            elif self.config.problem_type == "multi_label_classification":
                loss_fct = BCEWithLogitsLoss()
                loss = loss_fct(logits, labels)

        return Seq2SeqSequenceClassifierOutput(
            loss=loss,
            logits=logits,
            past_key_values=outputs.past_key_values,
            decoder_hidden_states=outputs.decoder_hidden_states,
            decoder_attentions=outputs.decoder_attentions,
            cross_attentions=outputs.cross_attentions,
            encoder_last_hidden_state=outputs.encoder_last_hidden_state,
            encoder_hidden_states=outputs.encoder_hidden_states,
            encoder_attentions=outputs.encoder_attentions,
        )


@auto_docstring
class BigBirdPegasusForQuestionAnswering(BigBirdPegasusPreTrainedModel):
    def __init__(self, config):
        super().__init__(config)

        config.num_labels = 2
        self.num_labels = config.num_labels

        self.model = BigBirdPegasusModel(config)
        self.qa_outputs = nn.Linear(config.hidden_size, config.num_labels)

        # Initialize weights and apply final processing
        self.post_init()

    @can_return_tuple
    @auto_docstring
    def forward(
        self,
        input_ids: torch.Tensor | None = None,
        attention_mask: torch.Tensor | None = None,
        decoder_input_ids: torch.LongTensor | None = None,
        decoder_attention_mask: torch.LongTensor | None = None,
        encoder_outputs: list[torch.FloatTensor] | None = None,
        start_positions: torch.LongTensor | None = None,
        end_positions: torch.LongTensor | None = None,
        inputs_embeds: torch.FloatTensor | None = None,
        decoder_inputs_embeds: torch.FloatTensor | None = None,
        use_cache: bool | None = None,
        **kwargs: Unpack[TransformersKwargs],
    ) -> tuple | Seq2SeqQuestionAnsweringModelOutput:
        r"""
        decoder_input_ids (`torch.LongTensor` of shape `(batch_size, target_sequence_length)`, *optional*):
            Provide for translation and summarization training. By default, the model will create this tensor by
            shifting the `input_ids` to the right, following the paper.
        decoder_attention_mask (`torch.LongTensor` of shape `(batch_size, target_sequence_length)`, *optional*):
            Default behavior: generate a tensor that ignores pad tokens in `decoder_input_ids`. Causal mask will also
            be used by default.

            If you want to change padding behavior, you should read
            [`modeling_bigbird_pegasus._prepare_decoder_attention_mask`] and modify to your needs. See diagram 1 in
            [the paper](https://huggingface.co/papers/1910.13461) for more information on the default strategy.
        """
        if start_positions is not None and end_positions is not None:
            use_cache = False

        outputs: Seq2SeqModelOutput = self.model(
            input_ids,
            attention_mask=attention_mask,
            decoder_input_ids=decoder_input_ids,
            decoder_attention_mask=decoder_attention_mask,
            encoder_outputs=encoder_outputs,
            inputs_embeds=inputs_embeds,
            decoder_inputs_embeds=decoder_inputs_embeds,
            use_cache=use_cache,
            **kwargs,
        )

        sequence_output = outputs[0]

        logits = self.qa_outputs(sequence_output)
        start_logits, end_logits = logits.split(1, dim=-1)
        start_logits = start_logits.squeeze(-1).contiguous()
        end_logits = end_logits.squeeze(-1).contiguous()

        total_loss = None
        if start_positions is not None and end_positions is not None:
            # If we are on multi-GPU, split add a dimension
            if len(start_positions.size()) > 1:
                start_positions = start_positions.squeeze(-1)
            if len(end_positions.size()) > 1:
                end_positions = end_positions.squeeze(-1)
            # sometimes the start/end positions are outside our model inputs, we ignore these terms
            ignored_index = start_logits.size(1)
            start_positions = start_positions.clamp(0, ignored_index)
            end_positions = end_positions.clamp(0, ignored_index)

            loss_fct = CrossEntropyLoss(ignore_index=ignored_index)
            start_loss = loss_fct(start_logits, start_positions)
            end_loss = loss_fct(end_logits, end_positions)
            total_loss = (start_loss + end_loss) / 2

        return Seq2SeqQuestionAnsweringModelOutput(
            loss=total_loss,
            start_logits=start_logits,
            end_logits=end_logits,
            past_key_values=outputs.past_key_values,
            decoder_hidden_states=outputs.decoder_hidden_states,
            decoder_attentions=outputs.decoder_attentions,
            cross_attentions=outputs.cross_attentions,
            encoder_last_hidden_state=outputs.encoder_last_hidden_state,
            encoder_hidden_states=outputs.encoder_hidden_states,
            encoder_attentions=outputs.encoder_attentions,
        )


# Copied from transformers.models.pegasus.modeling_pegasus.PegasusDecoderWrapper with Pegasus->BigBirdPegasus
class BigBirdPegasusDecoderWrapper(BigBirdPegasusPreTrainedModel):
    """
    This wrapper class is a helper class to correctly load pretrained checkpoints when the causal language model is
    used in combination with the [`EncoderDecoderModel`] framework.
    """

    def __init__(self, config):
        super().__init__(config)
        self.decoder = BigBirdPegasusDecoder(config)
        self.post_init()

    def forward(self, *args, **kwargs):
        return self.decoder(*args, **kwargs)


class BigBirdPegasusForCausalLM(BigBirdPegasusPreTrainedModel, GenerationMixin):
    def __init__(self, config):
        config.is_decoder = True
        config.is_encoder_decoder = False
        super().__init__(config)
        self.model = BigBirdPegasusDecoderWrapper(config)

        self.lm_head = nn.Linear(config.hidden_size, config.vocab_size, bias=False)

        # Initialize weights and apply final processing
        self.post_init()

    def get_input_embeddings(self):
        return self.model.decoder.embed_tokens

    def set_input_embeddings(self, value):
        self.model.decoder.embed_tokens = value

    @can_return_tuple
    @auto_docstring
    def forward(
        self,
        input_ids: torch.LongTensor | None = None,
        attention_mask: torch.Tensor | None = None,
        encoder_hidden_states: torch.FloatTensor | None = None,
        encoder_attention_mask: torch.FloatTensor | None = None,
        past_key_values: Cache | None = None,
        inputs_embeds: torch.FloatTensor | None = None,
        labels: torch.LongTensor | None = None,
        use_cache: bool | None = None,
        logits_to_keep: int | torch.Tensor = 0,
        **kwargs: Unpack[TransformersKwargs],
    ) -> tuple | CausalLMOutputWithCrossAttentions:
        r"""
        labels (`torch.LongTensor` of shape `(batch_size, sequence_length)`, *optional*):
            Labels for computing the masked language modeling loss. Indices should either be in `[0, ...,
            config.vocab_size]` or -100 (see `input_ids` docstring). Tokens with indices set to `-100` are ignored
            (masked), the loss is only computed for the tokens with labels in `[0, ..., config.vocab_size]`.

        Example:

        ```python
        >>> from transformers import AutoTokenizer, BigBirdPegasusForCausalLM

        >>> tokenizer = AutoTokenizer.from_pretrained("google/bigbird-pegasus-large-arxiv")
        >>> model = BigBirdPegasusForCausalLM.from_pretrained(
        ...     "google/bigbird-pegasus-large-arxiv"
        ... )
        >>> assert model.config.is_decoder, f"{model.__class__} has to be configured as a decoder."
        >>> inputs = tokenizer("Hello, my dog is cute", return_tensors="pt")
        >>> outputs = model(**inputs)

        >>> logits = outputs.logits
        ```"""

        outputs: BaseModelOutputWithPastAndCrossAttentions = self.model.decoder(
            input_ids=input_ids,
            attention_mask=attention_mask,
            encoder_hidden_states=encoder_hidden_states,
            encoder_attention_mask=encoder_attention_mask,
            past_key_values=past_key_values,
            inputs_embeds=inputs_embeds,
            use_cache=use_cache,
            **kwargs,
        )

        hidden_states = outputs[0]
        # Only compute necessary logits
        slice_indices = slice(-logits_to_keep, None) if isinstance(logits_to_keep, int) else logits_to_keep
        logits = self.lm_head(hidden_states[:, slice_indices, :])

        loss = None
        if labels is not None:
            labels = labels.to(logits.device)
            loss_fct = CrossEntropyLoss()
            loss = loss_fct(logits.view(-1, self.config.vocab_size), labels.view(-1))

        return CausalLMOutputWithCrossAttentions(
            loss=loss,
            logits=logits,
            past_key_values=outputs.past_key_values,
            hidden_states=outputs.hidden_states,
            attentions=outputs.attentions,
            cross_attentions=outputs.cross_attentions,
        )


__all__ = [
    "BigBirdPegasusForCausalLM",
    "BigBirdPegasusForConditionalGeneration",
    "BigBirdPegasusForQuestionAnswering",
    "BigBirdPegasusForSequenceClassification",
    "BigBirdPegasusModel",
    "BigBirdPegasusPreTrainedModel",
]
