Standardizing commenting style for major functions

[scap3yvt]

Fixes #798

Proposed Changes

• added function type help and docstring comments
• some raised errors have been changed to assertions for readability
• added variable types of function variables
• typing related updates for readability
  • tuple --> Tuple
  • list --> List
  • addition of Optional
• no functional changes to code

Checklist

• I have read the CONTRIBUTING guide.
• My PR is based from the current GaNDLF master .
• Non-breaking change (does not break existing functionality): provide as many details as possible for any breaking change.
• Function/class source code documentation added/updated.
• Code has been blacked for style consistency.
• If applicable, version information has been updated in GANDLF/version.py.
• If adding a git submodule, add to list of exceptions for black styling in pyproject.toml file.
• Usage documentation has been updated, if appropriate.
• Tests added or modified to cover the changes; if coverage is reduced, please give explanation.
• If customized dependency installation is required (i.e., a separate pip install step is needed for PR to be functional), please ensure it is reflected in all the files that control the CI, namely: python-test.yml, and all docker files [1,2,3].

[github-actions]

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[sarthakpati]

Seems like the comments have been added on some of the most important portions of the code, which is great start!

It would be good to expand this for metrics and losses as well and include that in this PR.

[szmazurek]

Hey there, thanks for the updates! I have commented on just few things regarding the typings for List type in few places (they maybe were skipped on purpose, if so it should be left as that).

[sarthakpati]

I am very happy with the way this PR has been worked out. Special thanks to the contributions of @Geeks-Sid and @szmazurek for helping review this 🦣 PR. 😄

[sarthakpati]

LGTM