code: def _get_ob(self):
      assert len(self.frames) == self.k
      return LazyFrames(list(self.frames))
  
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 4 for calling the FrameStack obj's underlying member method code with example usage: obj._get_ob() and returns: LazyFrames