code: def testMaxFramePooling(self):
      frame_skip = 2
      env = MockEnvironment()
      env = preprocessing.AtariPreprocessing(env, frame_skip=frame_skip)
      env.reset()
  
      # The first observation is 2, the second 0; max is 2.
      observation, _, _, _ = env.step(0)
      self.assertTrue((observation == 8).all())
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  from gym import core
  import numpy
  import tensorflow
  from tf_agents.environments import atari_preprocessing
label_desc: Use image node_id 4 for calling the AtariPreprocessingTest obj's underlying member method code with example usage: obj.testMaxFramePooling() without return types