    def test_RefResolver(self):
        """
        As of v4.18.0, RefResolver is fully deprecated.
        """

        message = "jsonschema.RefResolver is deprecated"
        with self.assertWarnsRegex(DeprecationWarning, message) as w:
            from jsonschema import RefResolver
        self.assertEqual(w.filename, __file__)

        with self.assertWarnsRegex(DeprecationWarning, message) as w:
            from jsonschema.validators import RefResolver  # noqa: F401
        self.assertEqual(w.filename, __file__)
As of v4.18.0, RefResolver is fully deprecated.
jsonschema/tests/test_deprecations.py