lowest_common_ancestor.py static type checking (#2329)

* adding static type checking to basic_binary_tree.py

* Add static type checking to functions with None return type

* Applying code review comments

* Added missing import statement

* fix spaciing

* "cleaned up depth_of_tree"

* Add doctests and then streamline display() and is_full_binary_tree()

* added static typing to lazy_segment_tree.py

* added missing import statement

* modified variable names for left and right elements

* added static typing to lowest_common_ancestor.py

* fixed formatting

* modified files to meet style guidelines, edited docstrings and added some doctests

* added and fixed doctests in lazy_segment_tree.py

* fixed errors in doctests

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