Improve Documentation for PQC and Expectation Layers (GH#238)

[Aniketsy]

This PR enhances the docstrings for the PQC and Expectation layers to comply with TensorFlow documentation standards.

Updates:
Added structured Args, Input shape, and Output shape sections to the class level docstrings.
Updated the call method docstrings with explicit Args and Returns sections, including types and tensor shapes.

Please let me know if this fix needs any improvements . I’m open to feedback and happy to make changes based on suggestions.
Thankyou!

[Aniketsy]

Hi @mhucka
I’ve pushed the changes for this issue and would like to request your review. I wasn’t able to run pre-commit run locally, so there might be some formatting errors. Please let me know if anything needs adjustment, and I’ll be happy to fix it.

[mhucka]

@Aniketsy Thank you for your work. There's one minor format issue I see right off: we're trying to keep to 80 character line lengths (see the .editorconfig configuration file). This is the reason why the CI check for formatting is failing (https://github.com/tensorflow/quantum/actions/runs/17688294620/job/50277418161?pr=895). Hopefully this won't be hard to fix up.

[Aniketsy]

@mhucka Thanks! I’ve fixed the format error and updated the PR. I’d also love to contribute to other issues, but I understand they are already assigned. Please feel free to point out any issues I could work on I’d be happy to take them on.

[mhucka]

@Aniketsy Thank you for your interest. I did a round of updates on all the issues and unassigned a couple. You don't necessarily have to take these on, but it would be hard to find which ones were unassigned, so I'll just list them here:

• format_check does not check notebook format #681
• Error in TFQ API Rendering 2: Electric Boogaloo #594

[mhucka]

This looks good. A couple of trivial requests. These are not about your changes but about the rest of the file, and I thought since you're fixing up the docstrings in this file, these could be done along the way:

• Super trivial: the docstring for the class Expectation has an extra empty line on line 229, which by docstring conventions shouldn't be there. Could you remove it?
• The docstring for __init__ lacks documentation for the kwargs argument. Could you add a description as part of this PR?

[mhucka]

Also, make sure to update the branch using the button in the GitHub interface. (If I do it, it may add my name to the PR, which I feel would be unfair.)

[Aniketsy]

Thanks! I’ve applied the changes based on your suggestions.