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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def infer(self, ob):
 """Add new observation to frame stack and infer policy. Args: ob: array of shape (height, width, channels) Returns: logits and vf. """

    self._add_to_stack(ob)
    logits, vf = self.infer_from_frame_stack(self._frame_stack)
    return logits, vf