def serialize(self):
        data = None
        if not self.type_:
            data = struct.pack('!B', self.type_)
        elif not self.len_:
            data = struct.pack(self._PACK_STR, self.type_, self.len_)
        else:
            form = self.len_ % "%ds"
            data = struct.pack(self._PACK_STR + form, self.type_,
                               self.len_, self.data)
        return data
dataset/ETHPy150Open osrg/ryu/ryu/lib/packet/ipv6.py/option.serialize/swapped operands of `%`