Internal" (IP as bytes, mask as int) to "machine" representation.

def i2m(self, pkt, i):
        """"Internal" (IP as bytes, mask as int) to "machine" representation."""  # noqa: E501
        mask, ip = i
        ip = pton_ntop.inet_pton(socket.AF_INET6, ip)
        return struct.pack(">B", mask) + ip[:self.mask2iplen(mask)]