[BUG][Python] Performance degredation in pathological case #23959

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• [n/a] Have you validated the input using an OpenAPI validator?
• [n/a] 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

#23958 describes the issue and I include my repro there https://gist.github.com/markjm/bb5805505d9dfddc5d595cadd0beaff1.

I am also making an issue as requested in the CONTRIBUTING build

openapi-generator version

I'm on an old version and patching my use-case but figured id contribute upstream because i see the issue in master.

Steps to reproduce

Just run the repro script!

Related issues/PRs

#18872 is similar but not quite the same

Suggest a fix