code: def _test_load_iqn(self, gpu):
      n_actions = 4
      q_func = pfrl.agents.iqn.ImplicitQuantileQFunction(
          psi=nn.Sequential(
              nn.Conv2d(4, 32, 8, stride=4),
              nn.ReLU(),
              nn.Conv2d(32, 64, 4, stride=2),
              nn.ReLU(),
              nn.Conv2d(64, 64, 3, stride=1),
              nn.ReLU(),
              nn.Flatten(),
          ),
          phi=nn.Sequential(
              pfrl.agents.iqn.CosineBasisLinear(64, 3136),
              nn.ReLU(),
          ),
          f=nn.Sequential(
              nn.Linear(3136, 512),
              nn.ReLU(),
              nn.Linear(512, n_actions),
          ),
      )
  
      # Use the same hyper parameters as https://arxiv.org/abs/1710.10044
      opt = torch.optim.Adam(
          q_func.parameters(), lr=5e-5, eps=1e-2 / 32
      )
  
      rbuf = replay_buffers.ReplayBuffer(100)
  
      explorer = explorers.LinearDecayEpsilonGreedy(
          start_epsilon=1.0,
          end_epsilon=0.1,
          decay_steps=10**6,
          random_action_func=lambda: np.random.randint(4),
      )
  
      agent = agents.IQN(
          q_func,
          opt,
          rbuf,
          gpu=gpu,
          gamma=0.99,
          explorer=explorer,
          replay_start_size=50,
          target_update_interval=10**4,
          update_interval=4,
          batch_accumulator="mean",
          phi=lambda x: x,
          quantile_thresholds_N=64,
          quantile_thresholds_N_prime=64,
          quantile_thresholds_K=32,
      )
  
      downloaded_model, exists = download_model(
          "IQN",
          "BreakoutNoFrameskip-v4",
          model_type=self.pretrained_type,
      )
      agent.load(downloaded_model)
      if os.environ.get("PFRL_ASSERT_DOWNLOADED_MODEL_IS_CACHED"):
          assert exists
  
imports: import os
  import numpy
  import pytest
  import torch
  from torch import nn
  import pfrl
  import pfrl.nn
  from pfrl import agents, explorers, replay_buffers
  from pfrl.initializers import init_chainer_default
  from pfrl.utils import download_model
label_desc: Use image node_id 2 for calling the TestLoadIQN obj's underlying member method code with example usage: obj._test_load_iqn(gpu) without return types