* Fix doubly linked list algorithm
* Fix bug with insert_at_tail method
Create __str__() method for Node class and LinkedList class
* Simplify __str__() of LinkedList
Returns empty string if there are no elements in the list
* Fix description
* spelling corrections
* review
* improved documentation, removed redundant variables, added testing
* added type hint
* camel case to snake case
* spelling fix
* review
* python --> Python # it is a brand name, not a snake
* explicit cast to int
* spaces in int list
* "!= None" to "is not None"
* Update comb_sort.py
* various spelling corrections in documentation & several variables naming conventions fix
* + char in file name
* import dependency - bug fix
Co-authored-by: John Law <johnlaw.po@gmail.com>