code: def setUp(self):
      super().setUp()
      self._model_fn = (
          lambda mode: tl.Serial(  # pylint: disable=g-long-lambda
              tl.Dense(64), tl.Relu(), tl.Dense(1)
          )
      )
      self._task = rl_task.RLTask(
          "CartPole-v0",
          gamma=0.5,
          max_steps=10,
          initial_trajectories=100,
      )
      self._trajectory_batch_stream = (
          self._task.trajectory_batch_stream(
              batch_size=256, epochs=[-1], max_slice_length=2
          )
      )
  
file_path: trax/trax/rl/value_tasks_test.py
imports: from absl.testing import absltest
  import numpy
  from trax import layers
  from trax import models
  from trax import optimizers
  from trax.rl import advantages
  from trax.rl import distributions
  from trax.rl import policy_tasks
  from trax.rl import task
  from trax.rl import value_tasks
  from trax.supervised import lr_schedules
  from trax.supervised import training
label_desc: Use image node_id 1 for calling the ValueTasksTest obj's underlying member method code with example usage: obj.setUp() without return types