Extend argument handling of do_execute with cell metadata

[jjvraw]

Enhances the do_execute method by allowing an optional cell_meta parameter, which represents cell metadata. This addition aligns with the Jupyter messaging protocol on metadata, which acknowledges the potential use of metadata in various message types.

Although metadata may not be often used, the capability to handle metadata within do_execute can expand the kernel's flexibility, especially in scenarios involving complex interactions or custom extensions, as detailed in the jupyter_client docs.

A noteable use case is in the development of Python wrapper kernels, where additional information might be passed via metadata to influence execution behavior, provide additional context, or interact with external services.

Changes:

• Extending the do_execute signature to include an optional metadata parameter
• Implementing logic in execute_request to extract and pass down cell metadata to do_execute
  • This involved expanding _accepts_cell_id to _accepts_parameters for broader parameter checks, which in turn seemly created nice flow in execute_request.

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It seemed bold requesting to replace cell_id with metadata despite one is derived from the other. However, _accepts_parameters enables flexible handling of these optional parameters, thus somewhat ensuring backward compatibility. A minor concern might involve the imports of _accepts_cell_id, which has been removed/replaced, but can be reintegrated if necessary.

Thanks

[jjvraw]

Hi,

I've noticed that all checks have passed on the PR except for "Test Prereleases". This seems to be related to an existing issue in pytest-asyncio, which might be causing the failure.

I am happy to work further on any specific actions or suggestions.

Thank you

[blink1073]

Thank you! I agree we should keep cell_id, but the private method name can be changed.