code: def add_arrow(self, x1, y1, x2, y2,  side='left',
                    shape='full', color='black',
                    width=0.01, head_width=0.03, overhang=0, **kws):
          
          dx, dy = x2-x1, y2-y1
  
          axes = self.axes
          if side == 'right':
              axes = self.get_right_axes()
          axes.arrow(x1, y1, dx, dy, shape=shape,
                     length_includes_head=True,
                     fc=color, edgecolor=color,
                     width=width, head_width=head_width,
                     overhang=overhang, **kws)
          self.draw()
docs: add arrow supplied x, y position