Corrected filename and include static types (#2440)

* Corrected name and include static types

- The name of the file is now compliant with python naming conventions
- Add static type as stated in contributing guidelines

* Apply suggestions from code review

- Delete documentation line to run doctests
- Delete type hints for variables that comes from functions

Co-authored-by: Christian Clauss <[email protected]>

* Add edge cases tests.

* print(f"{target} was {not_str}found in {sequence}")

Co-authored-by: Christian Clauss <[email protected]>