code: def plot(self, minx=-1.5, maxx=1.2, miny=-0.2, maxy=2, **kwargs):
          
          import matplotlib.pyplot as pp
          grid_width = max(maxx-minx, maxy-miny) / 200.0
  
          ax = kwargs.pop('ax', None)
  
          xx, yy = np.mgrid[minx:maxx:grid_width, miny:maxy:grid_width]
          V = self.potential(xx, yy)
          # clip off any values greater than 200, since they mess up
          # the color scheme
          if ax is None:
              ax = pp
  
          ax.contourf(xx, yy, V.clip(max=200), 40, **kwargs)
docs: Helper function to plot the Muller potential