code: def testOneStepUpdatesObservers(self):
      if tf.executing_eagerly():
          self.skipTest("b/123880556")
  
      env = tf_py_environment.TFPyEnvironment(
          driver_test_utils.PyEnvironmentMock()
      )
      policy = driver_test_utils.TFPolicyMock(
          env.time_step_spec(), env.action_spec()
      )
      policy_state_ph = tensor_spec.to_nest_placeholder(
          policy.policy_state_spec,
          default=0,
          name_scope="policy_state_ph",
          outer_dims=(1,),
      )
      num_episodes_observer = driver_test_utils.NumEpisodesObserver()
  
      driver = dynamic_step_driver.DynamicStepDriver(
          env, policy, observers=[num_episodes_observer]
      )
      run_driver = driver.run(policy_state=policy_state_ph)
  
      with self.session() as session:
          session.run(tf.compat.v1.global_variables_initializer())
          _, policy_state = session.run(run_driver)
          for _ in range(4):
              _, policy_state = session.run(
                  run_driver, feed_dict={policy_state_ph: policy_state}
              )
          self.assertEqual(
              self.evaluate(num_episodes_observer.num_episodes), 2
          )
  
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_step_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.specs import tensor_spec
  from tf_agents.utils import test_utils
label_desc: Use image node_id 1 for calling the DynamicStepDriverTest obj's underlying member method code with example usage: obj.testOneStepUpdatesObservers() without return types