NameError: name 'OneOfTransportInfoEndpoint' is not defined

Hi, hoping someone can help with this error:

Description

I am getting the following error when trying to run the python swagger stub:

python3 -m swagger_server
Traceback (most recent call last):
  File "/home/john/anaconda3/lib/python3.7/runpy.py", line 193, in _run_module_as_main
    "__main__", mod_spec)
  File "/home/john/anaconda3/lib/python3.7/runpy.py", line 85, in _run_code
    exec(code, run_globals)
  File "/home/john/api/stub/MecServiceMgmtApi/swagger_server/__main__.py", line 5, in <module>
    from swagger_server import encoder
  File "/home/john/api/stub/MecServiceMgmtApi/swagger_server/encoder.py", line 4, in <module>
    from swagger_server.models.base_model_ import Model
  File "/home/john/api/stub/MecServiceMgmtApi/swagger_server/models/__init__.py", line 50, in <module>
    from swagger_server.models.service_info import ServiceInfo
  File "/home/john/api/stub/MecServiceMgmtApi/swagger_server/models/service_info.py", line 18, in <module>
    from swagger_server.models.transport_info import TransportInfo  # noqa: F401,E501
  File "/home/john/api/stub/MecServiceMgmtApi/swagger_server/models/transport_info.py", line 20, in <module>
    class TransportInfo(Model):
  File "/home/john/api/stub/MecServiceMgmtApi/swagger_server/models/transport_info.py", line 25, in TransportInfo
    def __init__(self, id: TransportInfoId=None, name: TransportInfoName=None, description: TransportInfoDescription=None, type: TransportType=None, protocol: TransportInfoProtocol=None, version: TransportInfoVersion=None, endpoint: OneOfTransportInfoEndpoint=None, security: SecurityInfo=None, impl_specific_info: TransportInfoImplSpecificInfo=None):  # noqa: E501
NameError: name 'OneOfTransportInfoEndpoint' is not defined

Swagger-codegen version

swagger codegen: 3.0.24-SNAPSHOT
java: openjdk 11.0.9 2020-10-20

Command line used for generation

java -jar swagger-codegen-cli.jar generate -i json/MecServiceMgmtApi.json -l python-flask -o stub/MecServiceMgmtApi

OpenAPI JSON: https://forge.etsi.org/rep/mec/gs011-app-enablement-api

Steps to reproduce

python3 setup swagger_server

Start by reproducing the failure with the reported python3 -m swagger_server command and the supplied generation command. Inspect the generated swagger_server/models/transport_info.py, service_info.py, and models/__init__.py around OneOfTransportInfoEndpoint; done means the generated stub starts without this `NameError.