code: def observation(self, obs):
      if self._key is None:
          frame = obs
      else:
          frame = obs[self._key]
  
      if self._grayscale:
          frame = cv2.cvtColor(frame, cv2.COLOR_RGB2GRAY)
      frame = cv2.resize(
          frame,
          (self._width, self._height),
          interpolation=cv2.INTER_AREA,
      )
      if self._grayscale:
          frame = np.expand_dims(frame, -1)
  
      if self._key is None:
          obs = frame
      else:
          obs = obs.copy()
          obs[self._key] = frame
      return obs
  
imports: import numpy
  import os
  from collections import deque
  import gym
  from gym import spaces
  import cv2
  from .wrappers import TimeLimit
label_desc: Use image node_id 2 for calling the WarpFrame obj's underlying member method code with example usage: obj.observation(obs) and returns: obs