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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 iptag_set(self, iptag, addr, port, x, y):
 """Set the value of an IPTag. Forward SDP packets with the specified IP tag sent by a SpiNNaker application to a given external IP address. A :ref:`tutorial example <scp-and-sdp-tutorial>` of the use of IP Tags to send and receive SDP packets to and from applications is also available. Parameters iptag : int Index of the IPTag to set addr : string IP address or hostname that the IPTag should point at. port : int UDP port that the IPTag should direct packets to. """

        # Format the IP address
        ip_addr = struct.pack('!4B',
                              *map(int, socket.gethostbyname(addr).split('.')))
        self._send_scp(x, y, 0, SCPCommands.iptag,
                       int(consts.IPTagCommands.set) << 16 | iptag,
                       port, struct.unpack('<I', ip_addr)[0])