class_docstr: Ranking agent class.
code: def _variables_to_train(self):
      return self._scoring_network.trainable_variables
  
imports: import enum
  from typing import Optional, Text
  import tensorflow
  from tf_agents.agents import tf_agent
  from tf_agents.bandits.policies import ranking_policy
  from tf_agents.specs import bandit_spec_utils
  from tf_agents.trajectories import policy_step
  from tf_agents.trajectories import time_step
  from tf_agents.trajectories import trajectory
  from tf_agents.typing import types
  from tf_agents.utils import common
  from tf_agents.utils import eager_utils
  from tf_agents.utils import nest_utils
label_desc: Use image node_id 2 for calling the RankingAgent obj's underlying member method code with example usage: obj._variables_to_train() and returns: self