def convert_to_older_version(
            self, msg: AbstractInternalMessage) -> AbstractInternalMessage:
        msg_type = msg.MESSAGE_TYPE
        if msg_type not in self._MSG_TYPE_TO_OLD_MSG_CLASS_MAPPING:
            raise ValueError(
                f"Tried to convert unexpected new message type to v6: {msg_type}"
            )
        msg = cast(TxServiceSyncTxsMessage, msg)

        txs_content_short_ids = msg.txs_content_short_ids()
        txs_content_short_ids_v6 = [
            TxContentShortIdsV6(item.tx_hash, item.tx_content, item.short_ids)
            for item in txs_content_short_ids
        ]
        network_num = msg.network_num()

        return TxServiceSyncTxsMessageV6(network_num, txs_content_short_ids_v6)
    def convert_from_older_version(
            self, msg: AbstractInternalMessage) -> AbstractInternalMessage:
        msg_type = msg.MESSAGE_TYPE

        if msg_type not in self._MSG_TYPE_TO_NEW_MSG_CLASS_MAPPING:
            raise ValueError(
                f"Tried to convert unexpected old message type to v6: {msg_type}"
            )
        msg = cast(TxServiceSyncTxsMessageV6, msg)

        txs_content_short_ids_v6 = msg.txs_content_short_ids()
        txs_content_short_ids = [
            TxContentShortIds(
                item.tx_hash, item.tx_content, item.short_ids,
                [TransactionFlag.NO_FLAGS for _ in item.short_ids])
            for item in txs_content_short_ids_v6
        ]
        network_num = msg.network_num()

        return TxServiceSyncTxsMessage(network_num, txs_content_short_ids)