def store(self, client_id, user_id, transaction_id, data):
        transaction_id = b2a_hex(transaction_id)
        user = self._session.query(User) \
            .filter(User.client_id == client_id) \
            .filter(User.name == user_id).first()
        if user is None:
            user = User(user_id)
            user.client_id = client_id
            self._session.add(user)
        else:
            self._delete_expired()
            # Delete oldest transactions until we have room for one more.
            for transaction in user.transactions \
                    .offset(1 - self._max_transactions).all():
                self._session.delete(transaction)
        user.transactions.append(Transaction(transaction_id, data))
dataset/ETHPy150Open Yubico/u2fval/u2fval/core/transactiondb.py/DBStore.store/swapped operands of `-`