[BUG][Python] Syntax error in generated code with certain additionalProperties.

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?
• [Optional] Sponsorship to speed up the bug fix or feature request (example)

Description

Certain combinations of $ref and additionalProperties produces invalid Python.

openapi-generator version

Latest master

OpenAPI declaration file content or url

https://gist.github.com/jaklaassen-affirm/409fad729dd913427dde3aac86c9c751 contains the api.yaml that produces the error condition, the Python file showing the syntax error, and the Python file after applying the linked fix.

Generation Details

openapi-generator generate -g python -i api.yaml

Suggest a fix

This change fixed it for me: https://github.com/jaklaassen-affirm/openapi-generator/commit/74d1837ad50e78c43b98353a60a482704d5f608f. But I freely admit I don't understand the code well enough. Happy to write a test if someone can suggest the best way to test this and make a PR.

Thanks!

Start with the api.yaml and generated Python files in the linked gist, then reproduce the issue with openapi-generator generate -g python -i api.yaml. Compare the invalid output with the linked fix and locate the Python generator test coverage for this schema pattern. Done means the generated Python is syntactically valid and a regression test covers the $ref and additionalProperties combination.