[python][flask] Fix enum naming

[wing328]

• to fix [BUG][FLASK] enum name issue #16557
• add tests

PR checklist

• Read the contribution guidelines.
• Pull Request title clearly describes the work in the pull request and Pull Request description provides details about how to validate the work. Missing information here may result in delayed response from the community.
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  ./bin/generate-samples.sh
  ./bin/utils/export_docs_generators.sh
  

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  ./bin/utils/ensure-up-to-date
  

  Commit all changed files.
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[fleutot]

This solves the issue it aims to fix. Thank you!