def get_calibration(self) -> calibration.Calibration | None:
        """Returns the recorded calibration at the time when the job was run, if
        one was captured, else None."""
        status = self._inner_job().execution_status
        if not status.calibration_name:
            return None
        ids = engine_client._ids_from_calibration_name(status.calibration_name)
        response = self.context.client.get_calibration(*ids)
        metrics = v2.metrics_pb2.MetricsSnapshot.FromString(response.data.value)
        return calibration.Calibration(metrics)
Returns the recorded calibration at the time when the job was run, if
        one was captured, else None.
cirq-google/cirq_google/engine/engine_job.py