Miscellaneous style improvements to python_to_native_converter and compiler_cache, notably:

• enforce snake_case everywhere (for PEP8 compliance)
• separate public and private methods
• better docstrings and type hints for IDEs.

How Has This Been Tested?

pytest

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.