class_docstr: Mock environment for testing.
class_docstr_tok: ["Mock","environment","for","testing","."]
code: def step(self, action):
      self._observation += 1
      reward_multiplier = -1 if action > 0 else 1
      reward = self._observation * reward_multiplier
      is_terminal = self._observation >= self.max_steps
      self.game_over = is_terminal
  
      unused = 0
      return (self._observation, reward, is_terminal, unused)
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import os
  import shutil
  from absl import flags
  from dopamine.agents.dqn import dqn_agent
  from dopamine.agents.implicit_quantile import implicit_quantile_agent
  from dopamine.agents.rainbow import rainbow_agent
  from dopamine.discrete_domains import checkpointer
  from dopamine.discrete_domains import logger
  from dopamine.discrete_domains import run_experiment
  from dopamine.metrics import collector_dispatcher
  from dopamine.metrics import statistics_instance
  import gin.tf
  import mock
  import tensorflow
label_desc: Use image node_id 3 for calling the MockEnvironment obj's underlying member method code with example usage: obj.step(action) and returns: self,  reward,  is_terminal,  unused