[feature-enhancement-request] models.one_ofintegernumber for python-flask

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• 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?
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Description

Why do I have the error
ModuleNotFoundError: No module named 'openapi_server.models.one_ofintegernumber'

when running the python-flask generated stub ?
I was expecting it to lauch a http server like it does for the petstore exemple.

openapi-generator version

I'm using the version 5.3.0-SNAPSHOT (after trying with latest stable)

OpenAPI declaration file content or url

I use the yaml from https://docs.kraken.com/rest/ that I validated with https://apidevtools.org/swagger-parser/online/

https://gist.github.com/maliky/03de5e2a1664ec8df5a665c517d0d151

Generation Details

I cloned the git repertory, compiled to use the latest and ran

java -jar openapi-generator/modules/openapi-generator-cli/target/openapi-generator-cli.jar generate -g python-flask -i swagger-kraken-validated.json -o Og-latest-kraken -p legacyDiscriminatorBehavior=false 

then in a virtualenv with the requirements installed I run

python -m openapi_server

Full traceback

Traceback (most recent call last):
  File "/home/mlk/.pyenv/versions/3.8.2/lib/python3.8/runpy.py", line 193, in _run_module_as_main
    return _run_code(code, main_globals, None,
  File "/home/mlk/.pyenv/versions/3.8.2/lib/python3.8/runpy.py", line 86, in _run_code
    exec(code, run_globals)
  File "/home/mlk/Prog/Python/Crypto/API/Swagger-OpenAPI/Og-latest-kraken/openapi_server/__main__.py", line 5, in <module>
    from openapi_server import encoder
  File "/home/mlk/Prog/Python/Crypto/API/Swagger-OpenAPI/Og-latest-kraken/openapi_server/encoder.py", line 4, in <module>
    from openapi_server.models.base_model_ import Model
  File "/home/mlk/Prog/Python/Crypto/API/Swagger-OpenAPI/Og-latest-kraken/openapi_server/models/__init__.py", line 8, in <module>
    from openapi_server.models.asset_pair import AssetPair
  File "/home/mlk/Prog/Python/Crypto/API/Swagger-OpenAPI/Og-latest-kraken/openapi_server/models/asset_pair.py", line 9, in <module>
    from openapi_server.models.one_ofintegernumber import OneOfintegernumber
ModuleNotFoundError: No module named 'openapi_server.models.one_ofintegernumber'

Steps to reproduce

Try to generate server python-flask stub from the given json file.

Related issues/PRs

Did not find any

Suggest a fix

Looks like some typing hint not working as expected ?

Reproduce with the provided Kraken specification and the python-flask generation command, then inspect the generated openapi_server/models/asset_pair.py import and models/init.py loading path. Done means the generated package no longer imports a missing one_ofintegernumber module and python -m openapi_server can launch the server.