code: def hax(self):
          
          if make_axes_locatable is None:
              raise YellowbrickValueError((
                  "residuals histogram requires matplotlib 2.0.2 or greater "
                  "please upgrade matplotlib or set hist=False on the visualizer"
              ))
  
          divider = make_axes_locatable(self.ax)
  
          hax = divider.append_axes("right", size=1, pad=0.1, sharey=self.ax)
          hax.yaxis.tick_right()
          hax.grid(False, axis='x')
  
          return hax
docs: Returns the histogram axes, creating it only on demand.