def get_next_id(self):
        try:
            query = {'_id': 'last_id'}
            update = {'$inc': {'id': 1}}
            fn = self.db.internal.find_and_modify
            row = fn(query, update, upsert=True, new=True)
        except Exception as e:
            raise DatabaseException(e)
        return row['id']
def _verify_toplevel_json(self, replay_data):
        fn = self._filename

        if "version" not in replay_data:
            raise TransactionReplayError(fn, _('Missing key "{key}".'.format(key="version")))

        self._assert_type(replay_data["version"], str, "version", "string")

        _check_version(replay_data["version"], fn)