[python] Fix Circular imports on inherited discriminators.

[rc65]

This is a duplicate of #16809 as that seems to have been abandoned by the author.

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[wing328]

can you please add a test or two to modules/openapi-generator/src/test/resources/3_0/python/petstore-with-fake-endpoints-models-for-testing.yaml to cover the issue moving forward?

[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

[fa0311]

This Pull Request fails type parsing by mypy.

[rc65]

Closing in favour of #17886