def save(self, filename=None):
        filename = Path(filename) if filename is not None else self.filename
        with filename.open("w") as f:
            f.write(self.yaml)
def tag(self, g):
        self.g = g
        self.g.beginPath()
        self.g.fillText("%d, %d"%(self.x, self.y),self.x, self.y)
        self.g.stroke()