with patch("builtins.open", mock_open(read_data=NOT_TEST_CLASS_SOURCE)):
            with patch.object(assets.ast, "parse"):
                with patch.object(assets.FetchAssetHandler, "visit"):
                    with patch.object(assets.FetchAssetHandler, "generic_visit"):
                        handler = assets.FetchAssetHandler("fake_file.py", {})