code: def make_q_func(self, env):
      obs_size = env.observation_space.low.size
      hidden_size = 64
      return iqn.ImplicitQuantileQFunction(
          psi=nn.Sequential(
              nn.Linear(obs_size, hidden_size),
              nn.ReLU(),
          ),
          phi=nn.Sequential(
              pfrl.agents.iqn.CosineBasisLinear(32, hidden_size),
              nn.ReLU(),
          ),
          f=nn.Linear(hidden_size, env.action_space.n),
      )
  
imports: import basetest_dqn_like
  import numpy
  import pytest
  import torch
  from basetest_training import _TestBatchTrainingMixin
  from torch import nn
  import pfrl
  from pfrl.agents import iqn
  from pfrl.testing import torch_assert_allclose
label_desc: Use image node_id 2 for calling the TestIQNOnDiscreteABC obj's underlying member method code with example usage: obj.make_q_func(env) and returns: iqn