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 get_metrics(self):
        """Returns the stored metrics.

        The metrics are type checked against the set schema.

        Returns:
          Dictionary of metrics data in the format of the set schema.
        """
        artifact_utils.verify_schema_instance(self._schema, self._values)
        return self._values