def get_last_tid(self):
        try:
            spec = {'tid': {'$gt': 0}}
            sort = [('tid', -1)]
            row = self.db.docs.find_one(spec, sort=sort)
        except Exception as e:
            raise DatabaseException(e)
        if row:
            return row['tid']
        return 0
def __getattr__(self, name: str) -> Any:
        """Custom __getattr__ to allow access to metrics schema fields."""

        if name not in self._metric_fields:
            raise AttributeError('No field: {} in metrics.'.format(name))

        return self._values[name]