:param external_port: (int) external port to listen on
        :param protocol:      (str) 'UDP' | 'TCP'
        :return: None

async def delete_port_mapping(self, external_port: int, protocol: str) -> None:
        """
        :param external_port: (int) external port to listen on
        :param protocol:      (str) 'UDP' | 'TCP'
        :return: None
        """
        return await self.gateway.commands.DeletePortMapping(
            NewRemoteHost="", NewExternalPort=external_port, NewProtocol=protocol
        )