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**Description**

Related to the discussion here: https://github.com/apache/airflow/pull/8553#discussion_r416136954

Allow user to define expected terminal state. e.g. `JOB_STATE_CANCELLED` could be not treated as failure but expected terminal state.


<!-- A short description of your feature -->


"""
        Helper method to fetch the job metrics with the specified Job ID.
        :param job_id: Job ID to get.
        :return: the JobMetrics. See:
            https://cloud.google.com/dataflow/docs/reference/rest/v1b3/JobMetrics
        """
        result = (
            self._dataflow.projects()
            .locations()
            .jobs()
            .getMetrics(projectId=self._project_number, location=self._job_location, jobId=job_id)
            .execute(num_retries=self._num_retries)
        )
        self.log.debug("fetch_job_metrics_by_id %s:\n%s", job_id, result)
        return result
    def _fetch_list_job_messages_responses(self, job_id: str) -> Generator[dict, None, None]: