code: def test_single_agent_env(self):
      ev = RolloutWorker(
          env_creator=lambda _: MockEnv3(NUM_STEPS),
          default_policy_class=EchoPolicy,
          # Episode only works with env runner v1.
          config=AlgorithmConfig()
          .rollouts(enable_connectors=False)
          .rollouts(num_rollout_workers=0)
          .callbacks(LastInfoCallback),
      )
      ev.sample()
  
imports: import ray
  import unittest
  from typing import Dict, List, Optional, Union, Tuple
  import numpy
  from ray.rllib.algorithms.algorithm_config import AlgorithmConfig
  from ray.rllib.algorithms.callbacks import DefaultCallbacks
  from ray.rllib.env.multi_agent_env import MultiAgentEnv
  from ray.rllib.evaluation.rollout_worker import RolloutWorker
  from ray.rllib.evaluation.episode import Episode
  from ray.rllib.examples.env.mock_env import MockEnv3
  from ray.rllib.policy import Policy
  from ray.rllib.utils import override
  from ray.rllib.utils.typing import TensorStructType, TensorType
label_desc: Use image node_id 3 for calling the TestEpisodeLastValues obj's underlying member method code with example usage: obj.test_single_agent_env() without return types