ImportError: cannot import name 'cached_property' from 'werkzeug'

[smischke]

When running python3 install/setup.py I get the following error:

Traceback (most recent call last):
  File "/srv/lxc-rest/install/setup.py", line 3, in <module>
    import create_db
  File "/srv/lxc-rest/install/create_db.py", line 9, in <module>
    from app.models import *
  File "/srv/lxc-rest/app/__init__.py", line 6, in <module>
    from flask_restplus import Api
  File "/usr/local/lib/python3.9/dist-packages/flask_restplus/__init__.py", line 4, in <module>
    from . import fields, reqparse, apidoc, inputs, cors
  File "/usr/local/lib/python3.9/dist-packages/flask_restplus/fields.py", line 12, in <module>
    from werkzeug import cached_property
ImportError: cannot import name 'cached_property' from 'werkzeug' (/usr/lib/python3/dist-packages/werkzeug/__init__.py)

I'm on Debian 11. Any ideas?