class_docstr: An abstract asynchronous, vectorized environment.
  Used to batch data from multiple copies of an environment, so that
  each observation becomes an batch of observations, and expected action is a batch of actions to
  be applied per-environment.
class_docstr_tok: ["An","abstract","asynchronous",",","vectorized","environment",".","Used","to","batch","data","from","multiple","copies","of","an","environment",",","so","that","each","observation","becomes","an","batch","of","observations",",","and","expected","action","is","a","batch","of","actions","to","be","applied","per-environment","."]
code: def get_viewer(self):
      if self.viewer is None:
          from gym.envs.classic_control import rendering
  
          self.viewer = rendering.SimpleImageViewer()
      return self.viewer
  
imports: import contextlib
  import os
  from abc import ABC, abstractmethod
  from baselines.common.tile_images import tile_images
label_desc: Use image node_id 11 for calling the VecEnv obj's underlying member method code with example usage: obj.get_viewer() and returns: self