code: def observation(self, frame):
      frame = rgb2gray(frame)
      frame = resize(frame, height=self.height, width=self.width)
      return frame[:, :, None]
  
imports: from collections import deque
  import gymnasium
  from gymnasium import spaces
  import numpy
  from typing import Union
  from ray.rllib.utils.annotations import PublicAPI
  from ray.rllib.utils.images import rgb2gray, resize
label_desc: Use image node_id 2 for calling the WarpFrame obj's underlying member method code with example usage: obj.observation(frame) and returns: frame