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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 _decode_addr_key(self, obj_dict):
 """ Callback function to handle the decoding of the 'Addr' field. Serf msgpack 'Addr' as an IPv6 address, and the data needs to be unpack using socket.inet_ntop(). See: https://github.com/KushalP/serfclient-py/issues/20 :param obj_dict: A dictionary containing the msgpack map. :return: A dictionary with the correct 'Addr' format. """

        key = b'Addr'
        if key in obj_dict:
            try:
                # Try to convert a packed IPv6 address.
                # Note: Call raises ValueError if address is actually IPv4.
                ip_addr = socket.inet_ntop(socket.AF_INET6, obj_dict[key])

                # Check if the address is an IPv4 mapped IPv6 address:
                # ie. ::ffff:xxx.xxx.xxx.xxx
                if ip_addr.startswith('::ffff:'):
                    ip_addr = ip_addr.lstrip('::ffff:')

                obj_dict[key] = ip_addr.encode('utf-8')
            except ValueError:
                # Try to convert a packed IPv4 address.
                ip_addr = socket.inet_ntop(socket.AF_INET, obj_dict[key])
                obj_dict[key] = ip_addr.encode('utf-8')

        return obj_dict