docs: def restart(self, instance_id):
          """restarts a paused instance.
  
          :param str instance_id: instance identifier
  
          :return: None
          """
          try:
              if not self._paused:
                  log.debug("node %s is not paused, can't restart", instance_id)
                  return
              self._paused = False
              result = self._subscription._sms.start_role(
                  service_name=self._cloud_service._name,
                  deployment_name=self._cloud_service._name,
                  role_name=instance_id)
              self._subscription._wait_result(result)
          except Exception as exc:
              log.error('error restarting instance %s: %s', instance_id, exc)
              raise
          log.debug('restarted instance(instance_id=%s)', instance_id)