def test_str(self):
        """
        Calling C{str} on a version returns a human-readable string
        representation of the version.
        """
        self.assertEqual(str(Version("dummy", 1, 2, 3)),
                          "[dummy, version 1.2.3]")

        Calling C{str} on a version returns a human-readable string
        representation of the version.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/python/test/test_versions.py