code: def _subscribe_request(self, channel):
      cmd = pubsub_pb2.Command(
          channel_type=channel, subscribe_message={}
      )
      req = gcs_service_pb2.GcsSubscriberCommandBatchRequest(
          subscriber_id=self._subscriber_id,
          sender_id=self._worker_id,
          commands=[cmd],
      )
      return req
  
imports: import asyncio
  from collections import deque
  import logging
  import random
  from typing import Tuple, List
  import grpc
  from ray._private.utils import get_or_create_event_loop
  import ray._private.gcs_utils
  import ray._private.logging_utils
  from ray.core.generated.gcs_pb2 import ErrorTableData
  from ray.core.generated import dependency_pb2
  from ray.core.generated import gcs_service_pb2_grpc
  from ray.core.generated import gcs_service_pb2
  from ray.core.generated import common_pb2
  from ray.core.generated import pubsub_pb2
label_desc: Use image node_id 3 for calling the _SubscriberBase obj's underlying member method code with example usage: obj._subscribe_request(channel) and returns: req