code: def get_batch_id(batch, policy_id=DEFAULT_POLICY_ID):
      return batch.policy_batches[policy_id]["batch_id"][0]
  
file_path: ray/python/ray/rllib/utils/replay_buffers/tests/test_multi_agent_replay_buffer.py
imports: import unittest
  import numpy
  from ray.rllib.policy.sample_batch import SampleBatch, MultiAgentBatch, concat_samples
  from ray.rllib.policy.sample_batch import DEFAULT_POLICY_ID
  from ray.rllib.utils.replay_buffers.multi_agent_replay_buffer import MultiAgentReplayBuffer
  from ray.rllib.utils.replay_buffers.prioritized_replay_buffer import PrioritizedReplayBuffer
  from ray.rllib.utils.replay_buffers.replay_buffer import ReplayBuffer
label_desc: Use image node_id 1 for calling a global function with example usage: get_batch_id(batch, policy_id) and returns: batch