tests/test_regression.py::test_suite
  /usr/lib/python3.9/vendor-packages/_pytest/python.py:161: PytestReturnNotNoneWarning: Test functions should return None, but tests/test_regression.py::test_suite returned <class 'doctest._DocTestSuite'>.
  Did you mean to use `assert` instead of `return`?
  See https://docs.pytest.org/en/stable/how-to/assert.html#return-not-none for more information.
    warnings.warn(