code: def plot_model(self, proj, ax):
          
          x, y = proj
          y_vals = getattr(self.ig._eval_model(), y.name)
          x_vals = self.ig._x_points[x]
          plot, = ax.plot(x_vals, y_vals, c='red')
          return plot
docs: Plots the model proposed for the projection proj on ax.