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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 create(cls, name, min_dst_port, max_dst_port=None, min_src_port=None, max_src_port=None, protocol_agent=None, comment=None):
 """ Create the TCP service :param str name: name of tcp service :param int min_dst_port: minimum destination port value :param int max_dst_port: maximum destination port value :param int min_src_port: minimum source port value :param int max_src_port: maximum source port value :param str,ProtocolAgent protocol_agent: optional protocol agent for this service :param str comment: optional comment for service :raises CreateElementFailed: failure creating element with reason :return: instance with meta :rtype: TCPService """

        max_dst_port = max_dst_port if max_dst_port is not None else ''
        json = {'name': name,
                'min_dst_port': min_dst_port,
                'max_dst_port': max_dst_port,
                'min_src_port': min_src_port,
                'max_src_port': max_src_port,
                'protocol_agent_ref': element_resolver(protocol_agent) or None,
                'comment': comment}

        return ElementCreator(cls, json)