Returns an out-of-graph eval_fn using the Agent API.

def make_eval_fn_with_agent(
    agent_type, eval_mode, planner_hparams, model_dir, log_every_steps=None,
    video_writers=(), random_starts_step_limit=None
):
  """Returns an out-of-graph eval_fn using the Agent API."""
  def eval_fn(env, loop_hparams, policy_hparams, policy_dir, sampling_temp):
    """Eval function."""
    base_env = env
    env = rl_utils.BatchStackWrapper(env, loop_hparams.frame_stack_size)
    agent = make_agent_from_hparams(
        agent_type, base_env, env, loop_hparams, policy_hparams,
        planner_hparams, model_dir, policy_dir, sampling_temp, video_writers
    )

    if eval_mode == "agent_simulated":
      real_env = base_env.new_like(batch_size=1)
      stacked_env = rl_utils.BatchStackWrapper(
          real_env, loop_hparams.frame_stack_size
      )
      collect_frames_for_random_starts(
          real_env, stacked_env, agent, loop_hparams.frame_stack_size,
          random_starts_step_limit, log_every_steps
      )
      initial_frame_chooser = rl_utils.make_initial_frame_chooser(
          real_env, loop_hparams.frame_stack_size,
          simulation_random_starts=True,
          simulation_flip_first_random_for_beginning=False,
          split=None,
      )
      env_fn = rl.make_simulated_env_fn_from_hparams(
          real_env, loop_hparams, batch_size=loop_hparams.eval_batch_size,
          initial_frame_chooser=initial_frame_chooser, model_dir=model_dir
      )
      sim_env = env_fn(in_graph=False)
      env = rl_utils.BatchStackWrapper(sim_env, loop_hparams.frame_stack_size)

    kwargs = {}
    if not agent.records_own_videos:
      kwargs["video_writers"] = video_writers
    step_limit = base_env.rl_env_max_episode_steps
    if step_limit == -1:
      step_limit = None
    rl_utils.run_rollouts(
        env, agent, env.reset(), log_every_steps=log_every_steps,
        step_limit=step_limit, **kwargs
    )
    if eval_mode == "agent_real":
      assert len(base_env.current_epoch_rollouts()) == env.batch_size
  return eval_fn