docstr: Bin reward to {+1, 0, -1} by its sign.
code: def reward(self, reward):
      """Bin reward to {+1, 0, -1} by its sign."""
      return np.sign(reward)
  
imports: from collections import deque
  import gym
  import numpy
  from gym import spaces
  from packaging import version
  import pfrl
label_desc: Use image node_id 2 for calling the ClipRewardEnv obj's underlying member method code with example usage: obj.reward(reward) and returns: np