Refactor functions and update docstrings in functions_Helin_Harman.py

[helinHarman]

Updated function definitions and docstrings for clarity and compliance with Pytest requirements. Adjusted return types and removed unnecessary global declarations.

Describe your changes

Checklist

• I have read the [CONTRIBUTING]
• I have performed a self-review of my own code
• I have run the code locally and it works as expected
• I have commented my code, particularly in hard-to-understand areas

Screenshots (if appropriate)