python dependency python-socketio missing from ubuntu

The debian package python3-flask-socketio has an runtime dependency on the python package `python-socketio` (v.1.5+) that is not listed in https://packages.ubuntu.com/bionic/python3-flask-socketio.

    # py file is the example in https://github.com/miguelgrinberg/Flask-SocketIO
    $ export FLASK_APP=test_flask_socketio.py
    $ python3 -m flask run
    Traceback (most recent call last):
    ...
    pkg_resources.DistributionNotFound: The 'python-socketio>=1.5.0' distribution was not found and is required by the application

Confusingly, there is a debian package by the same name which is built from the python package 'gevent-socketio` (v.0.3.X).

Am I missing something? Is there something else I should be doing (other than a pip install python-socketio) to get this working?