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 __init__(self, test, nh, pmtu, table_id=0):
        self._test = test
        self.nh = nh
        self.pmtu = pmtu
        self.table_id = table_id