code: def testCriticLoss(self, create_critic_net_fn, skip_in_tf1):
      if skip_in_tf1 and not common.has_eager_been_enabled():
          self.skipTest(
              "Skipping test: sequential networks not supported in TF1"
          )
  
      critic_network = create_critic_net_fn()
      agent = sac_agent.SacAgent(
          self._time_step_spec,
          self._action_spec,
          critic_network=critic_network,
          actor_network=None,
          actor_optimizer=None,
          critic_optimizer=None,
          alpha_optimizer=None,
          actor_policy_ctor=DummyActorPolicy,
      )
  
      observations = tf.constant([[1, 2], [3, 4]], dtype=tf.float32)
      time_steps = ts.restart(observations, batch_size=2)
      actions = tf.constant([[5], [6]], dtype=tf.float32)
  
      rewards = tf.constant([10, 20], dtype=tf.float32)
      discounts = tf.constant([0.9, 0.9], dtype=tf.float32)
      next_observations = tf.constant(
          [[5, 6], [7, 8]], dtype=tf.float32
      )
      next_time_steps = ts.transition(
          next_observations, rewards, discounts
      )
  
      td_targets = [7.3, 19.1]
      pred_td_targets = [7.0, 10.0]
  
      self.evaluate(tf.compat.v1.global_variables_initializer())
  
      # Expected critic loss has factor of 2, for the two TD3 critics.
      expected_loss = self.evaluate(
          2
          * tf.compat.v1.losses.mean_squared_error(
              tf.constant(td_targets), tf.constant(pred_td_targets)
          )
      )
  
      loss = agent.critic_loss(
          time_steps,
          actions,
          next_time_steps,
          td_errors_loss_fn=tf.math.squared_difference,
      )
  
      self.evaluate(tf.compat.v1.global_variables_initializer())
      loss_ = self.evaluate(loss)
      self.assertAllClose(loss_, expected_loss)
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  from absl.testing import parameterized
  import mock
  import tensorflow
  from tf_agents.agents import test_util
  from tf_agents.agents.ddpg import critic_rnn_network
  from tf_agents.agents.sac import sac_agent
  from tf_agents.agents.sac import tanh_normal_projection_network
  from tf_agents.networks import actor_distribution_network
  from tf_agents.networks import actor_distribution_rnn_network
  from tf_agents.networks import nest_map
  from tf_agents.networks import network
  from tf_agents.networks import sequential
  from tf_agents.specs import tensor_spec
  from tf_agents.trajectories import policy_step
  from tf_agents.trajectories import time_step
  from tf_agents.trajectories import trajectory
  from tf_agents.utils import common
  from tf_agents.utils import test_utils
label_desc: Use image node_id 5 for calling the SacAgentTest obj's underlying member method code with example usage: obj.testCriticLoss(create_critic_net_fn, skip_in_tf1) without return types