code: def step(self, action):
          
          obs, rews, news, infos = self.env.step(action)
  
          self.ret = self.ret * self.gamma + rews
  
          obs = self._filter_observation(obs)
  
          if self.ret_rms:
              self.ret_rms.update(np.array([self.ret]))
              rews = np.clip(rews / np.sqrt(self.ret_rms.var + self.epsilon), -self.cliprew, self.cliprew)
  
          return obs, rews, news, infos
docs: Apply sequence of actions to sequence of environments
          actions -> (observations, rewards, news)
  
          where 'news' is a boolean vector indicating whether each element is new.