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 drawMe(self, g, r):
        self.g = g
        self.r = r
        self.g.save()
        self.g.moveTo(self.x,self.y)
        self.g.beginPath()
        # 根據 r 半徑繪製一個圓代表點的所在位置
        self.g.arc(self.x, self.y, self.r, 0, 2*math.pi, true)
        self.g.moveTo(self.x,self.y)
        self.g.lineTo(self.x+self.r, self.y)
        self.g.moveTo(self.x, self.y)
        self.g.lineTo(self.x-self.r, self.y)
        self.g.moveTo(self.x, self.y)
        self.g.lineTo(self.x, self.y+self.r)
        self.g.moveTo(self.x, self.y)
        self.g.lineTo(self.x, self.y-self.r)
        self.g.restore()
        self.g.stroke()