convert function docstrings to numpydoc style

[mohitulm]

This PR has docstrings converted from the current format to the standard numpydoc style format

Description

The conversion has been done automatically with scripts and then manually inspected. No changes have been made to the code. Some cases, such as where no additional information is present apart from the parameter's name or an empty return, have been omitted to reduce ambiguity. All the information is preserved.

Motivation and Context

To have a fixed standard for docstrings.

How Has This Been Tested?

This has been tested with the current testing framework.

Types of changes

• Bug fix
• New feature
• Breaking change (Causes existing functionality to not work as expected)

Checklist:

• My code follows the code style of this project.
• I have documented my changes in /docs/changelog.md.
• My change requires additional/updated documentation.
• I have updated the documentation accordingly.
• I have added/updated the config example for any module docstrings as necessary.
• I have checked that the change does not contain obvious errors
  (syntax, indentation, mutable default values, etc.).
• I have tested my changes using 'Load all modules' on the default dummy configuration.
• All changed Jupyter notebooks have been stripped of their output cells.