def set_label(self, s, label):
        self.state.body_labels[self.bodies[self.index].segment_id] = label
        self.set_index(self.index + 1)
def EVT_MOUSEWHEEL(event):
  global zoomdist
  dy = event.WheelRotation
  zoomdist *= np.power(0.95, -dy)
  refresh()