class_docstr: Stochastically flicker frames.
code: def observation(self, observation):
      if self.unwrapped.np_random.rand() < 0.5:
          return np.zeros_like(observation)
      else:
          return observation
  
imports: from collections import deque
  import gym
  import numpy
  from gym import spaces
  import chainerrl
label_desc: Use image node_id 2 for calling the FlickerFrame obj's underlying member method code with example usage: obj.observation(observation) and returns: np, observation