code: def testCustomRewardFn(self):
      obs_spec = array_spec.BoundedArraySpec((2, 3), np.int32, -10, 10)
      batch_size = 3
      env = random_py_environment.RandomPyEnvironment(
          obs_spec,
          reward_fn=lambda *_: np.ones(batch_size),
          batch_size=batch_size,
      )
      env._done = False
      env.reset()
      time_step = env.step([0])  # pytype: disable=wrong-arg-types
      self.assertSequenceAlmostEqual([1.0] * 3, time_step.reward)
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  from absl.testing import parameterized
  import numpy
  from tf_agents.environments import random_py_environment
  from tf_agents.specs import array_spec
  from tf_agents.utils import test_utils
label_desc: Use image node_id 8 for calling the RandomPyEnvironmentTest obj's underlying member method code with example usage: obj.testCustomRewardFn() without return types