def insert_pt(self, new_pt):
    'returns index of new point'
    i = bisect(self.points, (new_pt[0], None))
    self.points.insert(i, new_pt)
    dispatcher.send('points changed', sender=self)
    return i
returns index of new point
def insert_pt(self, new_pt):
    
    i = bisect(self.points, (new_pt[0], None))
    self.points.insert(i, new_pt)
    dispatcher.send('points changed', sender=self)
    return i