def serialize(self, buf, offset):
        # fixup
        data = self.data
        if data is None:
            data = bytearray()
        self.len = (utils.round_up(len(data), 8) +
                    ofproto.OFP_ACTION_EXPERIMENTER_HEADER_SIZE)
        super(OFPActionExperimenterUnknown, self).serialize(buf, offset)
        msg_pack_into(len(self.data) % '!%ds',
                      buf,
                      offset + ofproto.OFP_ACTION_EXPERIMENTER_HEADER_SIZE,
                      self.data)
dataset/ETHPy150Open osrg/ryu/ryu/ofproto/ofproto_v1_4_parser.py/OFPActionExperimenterUnknown.serialize/swapped operands of `%`