[Python] fix object arrays giving mypy error "Incompatible types in assignment" in to_dict()

[VelorumS]

The generated to_dict() function uses the same variable to iterate over arrays of different types. Use different variables instead.

Added "MultiArrays" to the python petstore sample. It has two arrays of objects: tags and files. This triggers the mypy error.

fix #19214

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@cbornet @tomplus @krjakbrjak @fa0311 @multani

[multani]

LGTM 👍

[wing328]

Thanks for the PR but your commit (as shown in the Commits tab) is not linked to your Github account, which means this PR won't count as your contribution in https://github.com/OpenAPITools/openapi-generator/graphs/contributors.

Let me know if you need help fixing it.

Ref: https://github.com/OpenAPITools/openapi-generator/wiki/FAQ#how-can-i-update-commits-that-are-not-linked-to-my-github-account

[VelorumS]

Thank you. Added the email, replaced the test with a separate "MultiArrays" object that shouldn't break the Pet tests.

[multani]

LGTM 👍