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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 ack(self):
 """Acknowledge the given message. Acknowledging a message in Pub/Sub means that you are done with it, and it will not be delivered to this subscription again. You should avoid acknowledging messages until you have *finished* processing them, so that in the event of a failure, you receive the message again. .. warning:: Acks in Pub/Sub are best effort. You should always ensure that your processing code is idempotent, as you may receive any given message more than once. """

        time_to_ack = math.ceil(time.time() - self._received_timestamp)
        self._request_queue.put(
            requests.AckRequest(
                ack_id=self._ack_id, byte_size=self.size, time_to_ack=time_to_ack
            )
        )