code: def identity_collate(batch):
      assert isinstance(batch, list) and len(batch) == 1, f"Got {batch}"
      return batch[0]
  
imports: import logging
  import os
  import pprint
  import unittest
  import uuid
  import numpy
  import pytest
  import pytorch_lightning
  import torch
  from parameterized import parameterized
  from reagent.gym.agents.agent import Agent
  from reagent.gym.datasets.replay_buffer_dataset import OfflineReplayBufferDataset
  from reagent.gym.envs import Gym
  from reagent.gym.policies.random_policies import make_random_policy_for_env
  from reagent.gym.runners.gymrunner import evaluate_for_n_episodes
  from reagent.gym.utils import build_normalizer, fill_replay_buffer
  from reagent.model_managers.union import ModelManager__Union
  from reagent.replay_memory.circular_replay_buffer import ReplayBuffer
  from reagent.test.base.horizon_test_base import HorizonTestBase
  from reagent.workflow.types import RewardOptions
label_desc: Use image node_id 2 for calling a global function with example usage: identity_collate(batch) and returns: batch