code: def testLoss(self):
      agent = greedy_multi_objective_agent.GreedyMultiObjectiveNeuralAgent(
          self._time_step_spec,
          self._action_spec,
          self._scalarizer,
          objective_network_and_loss_fn_sequence=self._create_objective_network_and_loss_fn_sequence(),
          optimizer=None,
      )
      observations = np.array([[1, 2], [3, 4]], dtype=np.float32)
      actions = np.array([0, 1], dtype=np.int32)
      objectives = np.array(
          [[8, 12, 11], [25, 18, 32]], dtype=np.float32
      )
      initial_step, final_step = _get_initial_and_final_steps(
          observations, objectives
      )
      action_step = _get_action_step(actions)
      experience = _get_experience(
          initial_step, action_step, final_step
      )
  
      init_op = agent.initialize()
      if not tf.executing_eagerly():
          with self.cached_session() as sess:
              common.initialize_uninitialized_variables(sess)
              self.assertIsNone(sess.run(init_op))
      loss, _ = agent._loss(experience)
      self.evaluate(tf.compat.v1.initialize_all_variables())
      self.assertAllClose(self.evaluate(loss), 0.0)
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import collections
  from typing import List, Tuple
  import numpy
  import tensorflow
  from tf_agents.bandits.agents import greedy_multi_objective_neural_agent
  from tf_agents.bandits.drivers import driver_utils
  from tf_agents.bandits.multi_objective import multi_objective_scalarizer
  from tf_agents.bandits.networks import global_and_arm_feature_network
  from tf_agents.bandits.networks import heteroscedastic_q_network
  from tf_agents.bandits.specs import utils
  from tf_agents.networks import network
  from tf_agents.policies import utils
  from tf_agents.specs import array_spec
  from tf_agents.specs import tensor_spec
  from tf_agents.trajectories import policy_step
  from tf_agents.trajectories import time_step
  from tf_agents.typing import types
  from tf_agents.utils import common
label_desc: Use image node_id 8 for calling the MultiObjectiveAgentTest obj's underlying member method code with example usage: obj.testLoss() without return types