def __missing__(self, key):
        if self.default_factory is None:
            raise KeyError(key)
        else:
            ret = self[key] = self.default_factory(name=key)
            return ret
def drawMe(self, g):
        self.g = g
        self.g.beginPath()
        self.g.moveTo(self.p1.x,self.p1.y)
        self.g.lineTo(self.p2.x,self.p2.y)
        self.g.stroke()