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 active_at_datetime(self, deadline):
        """Check whether the verification was active at a particular datetime.

        Arguments:
            deadline (datetime): The date at which the verification was active
                (created before and expiration datetime is after today).

        Returns:
            bool

        """
        return (
            self.created_at < deadline and
            self.expiration_datetime > now()
        )