DOC: Fix docstrings in gradient.py

[hsinfan1996]

Motivation for these changes

Fix docstrings that are not formatted correctly.
Closes #414

Implementation details

According to https://numpydoc.readthedocs.io/en/latest/format.html#returns, return type is always required. Missing return types are added to gradient.py grad Lop and Rop.

Checklist

• Explain motivation and implementation 👆
• Make sure that the pre-commit linting/style checks pass.
• Link relevant issues, preferably in nice commit messages.
• The commits correspond to relevant logical changes. Note that if they don't, we will rewrite/rebase/squash the git history before merging.
• Are the changes covered by tests and docstrings?
• Fill out the short summary sections 👇

Major / Breaking Changes

• No

New features

• No

Bugfixes

• No

Documentation

• ...

Maintenance

• ...

[OriolAbril]

This is an improvement, but the docstring might need a more thorough review. In the description (line 205) it says:

"If wrt is a list/tuple, then return a list/tuple with the results."

But in lines 355-357 it's f what is checked to match its output type. I also don't know how common Variable is, it might be worth to use https://www.sphinx-doc.org/en/master/usage/extensions/napoleon.html#confval-napoleon_type_aliases for Variable so it is easier to write but still keep the hyperlink.

[hsinfan1996]

Actually I am not too familiar with the code itself.

[ricardoV94]

"If wrt is a list/tuple, then return a list/tuple with the results."

You're right. This is correct for the grad but not L_op and R_op, so we should fix the docstrings of those.

I also don't know how common Variable is,

Quite common, after TensorVariable. @hsinfan1996 is this something you want to take a stab at? No problem if not, we can open a separate issue for it.

[hsinfan1996]

For L_op and R_op, if it is as simple as removing line 205 and 394, then I can do it. If not, I am afraid I will not be able to take care of the rest.

[ricardoV94]

For L_op and R_op, if it is as simple as removing line 205 and 394, then I can do it. If not, I am afraid I will not be able to take care of the rest.

I think the correct thing would be: "If f is a list/tuple, then return a list/tuple with the results."

[hsinfan1996]

For L_op and R_op, if it is as simple as removing line 205 and 394, then I can do it. If not, I am afraid I will not be able to take care of the rest.

I think the correct thing would be: "If f is a list/tuple, then return a list/tuple with the results."

Got it.

[hsinfan1996]

Is there something preventing us from proceeding with this PR?

[ricardoV94]

Is there something preventing us from proceeding with this PR?

I didn't realize you had fixed the Rop already. Should be good to go

[ricardoV94]

Thanks @hsinfan1996