docs: def on_motion(self, event):
          'on motion we will move the rect if the mouse is over us'
          if self.press is None:
              return
  
          if event.inaxes != self.ax:
              return
          # print(event.inaxes)
  
          x0, y0, btn = self.press
          x0.append(event.xdata)
          y0.append(event.ydata)