Add docstrings to Python functions

[hackersifu]

The functions, specifically within the T&S model Python code, could use docstrings, to better help with code reviews and potential PRs.

[Abastien1734]

LGTM

[babuloseo]

based

[aloiscochard]

@hackersifu it is not a priority at the moment.

That being said we are really thankful for the shiny looking issue you created here, feel free to follow us on Twitter.

You could also do the work in your own f()rk.