Make generated Python files `mypy` error-free

[shunichironomura]

Description

When running mypy on marimo notebooks, mypy reports error: Name "__" already defined on line X [no-redef] errors because cells in marimo notebooks are all defined as functions with the same name: __. This makes it difficult to properly type-check marimo notebooks.

Suggested solution

There are at least three approaches to resolve this:

1. Define cells as functions with unique names. This approach eradicates the root cause, but possibly has side effects causing other issues.
2. Add # type: ignore[no-redef] comments to lines containing @app.cell to suppress errors. This approach has probably the fewest side effects but makes the files a bit noisy.
3. Add a top-level #mypy: disable-error-code="no-redef" comment. This approach is probably the least noisy but possibly suppresses other no-redef errors in the file.

Alternative

No response

Additional context

As far as I know, there is no way to configure mypy to ignore a certain error in specific files (like per-file-ignores config in Ruff) via configuration files such as pyproject.toml. So it's impossible to suppress the no-redef errors in marimo notebooks without modifying the notebook files.

So my current workaround is to take approach 3 and manually adding the top-level #mypy: disable-error-code="no-redef" comment to every marimo notebook.