As discussed in  https://github.com/apache/airflow/pull/15534#discussion_r620500075, we could possibly rewrite Beam Hook to remove the need of storing state in it.
with pytest.warns(DeprecationWarning, match="This method is deprecated"):
            self.dataflow_hook.start_python_dataflow(
                job_name=JOB_NAME,
                variables=DATAFLOW_VARIABLES_PY,
                dataflow=PY_FILE,
                py_options=PY_OPTIONS,
                py_interpreter=DEFAULT_PY_INTERPRETER,
                py_requirements=py_requirements,
                on_new_job_id_callback=on_new_job_id_callback,
            )
        expected_variables = copy.deepcopy(DATAFLOW_VARIABLES_PY)
        expected_variables["job_name"] = job_name
        expected_variables["region"] = DEFAULT_DATAFLOW_LOCATION
        mock_callback_on_job_id.assert_called_once_with(on_new_job_id_callback)
        mock_beam_start_python_pipeline.assert_called_once_with(
            variables=expected_variables,
            py_file=PY_FILE,
            py_interpreter=DEFAULT_PY_INTERPRETER,
            py_options=PY_OPTIONS,
            py_requirements=py_requirements,
            py_system_site_packages=False,
            process_line_callback=mock_callback_on_job_id.return_value,
        )
        mock_dataflow_wait_for_done.assert_called_once_with(
            job_id=mock.ANY, job_name=job_name, location=DEFAULT_DATAFLOW_LOCATION
        )
    @mock.patch(DATAFLOW_STRING.format("uuid.uuid4"))
    @mock.patch(DATAFLOW_STRING.format("DataflowHook.wait_for_done"))
    @mock.patch(DATAFLOW_STRING.format("process_line_and_extract_dataflow_job_id_callback"))
    def test_start_python_dataflow_with_custom_region_as_variable(