code: def infer(self, ob):
      
      self._add_to_stack(ob)
      logits, vf = self.infer_from_frame_stack(self._frame_stack)
      return logits, vf
docs: Add new observation to frame stack and infer policy.
  
      Args:
        ob: array of shape (height, width, channels)
  
      Returns:
        logits and vf.