code: def tearDownClass(cls):
      ray.shutdown()
  
imports: import unittest
  import numpy
  import ray
  import ray.rllib.algorithms.ppo
  from ray.rllib.algorithms.ppo.ppo import LEARNER_RESULTS_CURR_ENTROPY_COEFF_KEY
  from ray.rllib.algorithms.callbacks import DefaultCallbacks
  from ray.rllib.algorithms.ppo.tests.test_ppo import PENDULUM_FAKE_BATCH
  from ray.rllib.core.learner.learner import LEARNER_RESULTS_CURR_LR_KEY
  from ray.rllib.evaluation.postprocessing import compute_gae_for_sample_batch
  from ray.rllib.policy.sample_batch import DEFAULT_POLICY_ID
  from ray.rllib.utils.metrics.learner_info import LEARNER_INFO
  from ray.rllib.utils.test_utils import check, check_compute_single_action, check_train_results, framework_iterator
label_desc: Use image node_id 2 for calling the TestPPO obj's underlying member method code with example usage: obj.tearDownClass(cls) without return types