code: def testOneStepReplayBufferObservers(self):
      env = tf_py_environment.TFPyEnvironment(
          driver_test_utils.PyEnvironmentMock()
      )
      policy = driver_test_utils.TFPolicyMock(
          env.time_step_spec(), env.action_spec()
      )
      replay_buffer = driver_test_utils.make_replay_buffer(policy)
  
      driver = dynamic_episode_driver.DynamicEpisodeDriver(
          env,
          policy,
          num_episodes=1,
          observers=[replay_buffer.add_batch],
      )
  
      run_driver = (
          driver.run if tf.executing_eagerly() else driver.run()
      )
  
      self.evaluate(tf.compat.v1.global_variables_initializer())
  
      for _ in range(3):
          self.evaluate(run_driver)
  
      trajectories = self.evaluate(replay_buffer.gather_all())
  
      self.assertAllEqual(
          trajectories.step_type, [[0, 1, 2, 0, 1, 2, 0, 1, 2]]
      )
      self.assertAllEqual(
          trajectories.action, [[1, 2, 1, 1, 2, 1, 1, 2, 1]]
      )
      self.assertAllEqual(
          trajectories.observation, [[0, 1, 3, 0, 1, 3, 0, 1, 3]]
      )
      self.assertAllEqual(
          trajectories.policy_info, [[2, 4, 2, 2, 4, 2, 2, 4, 2]]
      )
      self.assertAllEqual(
          trajectories.next_step_type, [[1, 2, 0, 1, 2, 0, 1, 2, 0]]
      )
      self.assertAllEqual(
          trajectories.reward,
          [[1.0, 1.0, 0.0, 1.0, 1.0, 0.0, 1.0, 1.0, 0.0]],
      )
      self.assertAllEqual(
          trajectories.discount,
          [[1.0, 0.0, 1, 1, 0, 1.0, 1.0, 0.0, 1.0]],
      )
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import numpy
  import tensorflow
  from tf_agents.bandits.environments import environment_utilities
  from tf_agents.bandits.environments import stationary_stochastic_py_environment
  from tf_agents.drivers import dynamic_episode_driver
  from tf_agents.drivers import test_utils
  from tf_agents.environments import tf_py_environment
  from tf_agents.policies import random_tf_policy
  from tf_agents.replay_buffers import tf_uniform_replay_buffer
  from tf_agents.utils import test_utils
label_desc: Use image node_id 6 for calling the DynamicEpisodeDriverTest obj's underlying member method code with example usage: obj.testOneStepReplayBufferObservers() without return types