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, p1, p2):
        self.p1 = p1
        self.p2 = p2
        self.length = math.sqrt(math.pow((self.p2.x - self.p1.x), 2) + math.pow((self.p2.y - self.p1.y), 2))