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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 subscribe(self, destination, id=None, ack='auto', headers=None, **keyword_headers):
 """ Subscribe to a destination. :param str destination: the topic or queue to subscribe to :param str id: a unique id to represent the subscription :param str ack: acknowledgement mode, either auto, client, or client-individual (see http://stomp.github.io/stomp-specification-1.2.html#SUBSCRIBE_ack_Header) for more information :param dict headers: a map of any additional headers the broker requires :param keyword_headers: any additional headers the broker requires """

        assert destination is not None, "'destination' is required"
        headers = utils.merge_headers([headers, keyword_headers])
        headers[HDR_DESTINATION] = destination
        if id:
            headers[HDR_ID] = id
        headers[HDR_ACK] = ack
        self.send_frame(CMD_SUBSCRIBE, headers)