Changes the code To return the list in dynamic_programming/subset_generation.py (#10191)

* Changing the code to return tuple

* Changing the code to return tuple

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* Update dynamic_programming/subset_generation.py

Co-authored-by: Christian Clauss <cclauss@me.com>

* Adding doctests in subset_generation.py

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* Update subset_generation.py

* Update subset_generation.py

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* Update subset_generation.py

* Update subset_generation.py

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* Update dynamic_programming/subset_generation.py

Co-authored-by: Christian Clauss <cclauss@me.com>

* Update stock_span_problem.py

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* Update subset_generation.py

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* Update subset_generation.py

* Update subset_generation.py

* Update subset_generation.py

* Update subset_generation.py

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Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Christian Clauss <cclauss@me.com>