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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 receive_datagram(self, args):
 """ Handle messages coming from the udp socket. :param args: (data, client_address) """

        data, client_address = args

        serializer = Serializer()
        message = serializer.deserialize(data, client_address)
        if isinstance(message, int):
            logger.error("receive_datagram - BAD REQUEST")

            rst = Message()
            rst.destination = client_address
            rst.type = defines.Types["RST"]
            rst.code = message
            self.send_datagram(rst)
            return
        logger.debug("receive_datagram - " + str(message))
        if isinstance(message, Request):

            transaction = self._messageLayer.receive_request(message)

            if transaction.request.duplicated and transaction.completed:
                logger.debug("message duplicated,transaction completed")
                transaction = self._observeLayer.send_response(transaction)
                transaction = self._blockLayer.send_response(transaction)
                transaction = self._messageLayer.send_response(transaction)
                self.send_datagram(transaction.response)
                return
            elif transaction.request.duplicated and not transaction.completed:
                logger.debug("message duplicated,transaction NOT completed")
                self._send_ack(transaction)
                return

            transaction.separate_timer = self._start_separate_timer(transaction)

            transaction = self._blockLayer.receive_request(transaction)

            if transaction.block_transfer:
                self._stop_separate_timer(transaction.separate_timer)
                transaction = self._messageLayer.send_response(transaction)
                self.send_datagram(transaction.response)
                return

            transaction = self._observeLayer.receive_request(transaction)

            """
            call to the cache layer to check if there's a cached response for the request
            if not, call the forward layer
            """
            if self._cacheLayer is not None:
                transaction = self._cacheLayer.receive_request(transaction)

                if transaction.cacheHit is False:
                    logger.debug(transaction.request)
                    transaction = self._forwardLayer.receive_request_reverse(transaction)
                    logger.debug(transaction.response)

                transaction = self._observeLayer.send_response(transaction)

                transaction = self._blockLayer.send_response(transaction)

                transaction = self._cacheLayer.send_response(transaction)
            else:
                transaction = self._forwardLayer.receive_request_reverse(transaction)

                transaction = self._observeLayer.send_response(transaction)

                transaction = self._blockLayer.send_response(transaction)

            self._stop_separate_timer(transaction.separate_timer)

            transaction = self._messageLayer.send_response(transaction)

            if transaction.response is not None:
                if transaction.response.type == defines.Types["CON"]:
                    self._start_retrasmission(transaction, transaction.response)
                self.send_datagram(transaction.response)

        elif isinstance(message, Message):
            transaction = self._messageLayer.receive_empty(message)
            if transaction is not None:
                transaction = self._blockLayer.receive_empty(message, transaction)
                self._observeLayer.receive_empty(message, transaction)

        else:  # pragma: no cover
            logger.error("Received response from %s", message.source)