code: def __call__(self, reward):
      self.average_reward *= 1 - self.tau
      self.average_reward += self.tau * reward
      return reward - self.average_reward
  
file_path: chainerrl/chainerrl/misc/reward_filter.py
label_desc: Use image node_id 2 for calling the AverageRewardFilter obj's underlying member method code with example usage: obj.__call__(reward) and returns: unknown