code: def make_plot(self):
          
  
          self.get_contour_values()
          # sets levels of main contour plot
          colors1 = ['blue', 'green', 'red', 'purple', 'orange',
                     'gold', 'magenta']
  
          # set contour value. Default is SNR_CUT.
          self.snr_contour_value = (self.SNR_CUT if self.snr_contour_value is None
                                    else self.snr_contour_value)
  
          # plot contours
          for j in range(len(self.zvals)):
              hz = self.axis.contour(self.xvals[j], self.yvals[j],
                                     self.zvals[j], np.array([self.snr_contour_value]),
                                     colors=colors1[j], linewidths=1., linestyles='solid')
  
              # plot invisible lines for purpose of creating a legend
              if self.legend_labels != []:
                  # plot a curve off of the grid with same color for legend label.
                  self.axis.plot([0.1, 0.2], [0.1, 0.2], color=colors1[j],
                                 label=self.legend_labels[j])
  
          if self.add_legend:
              self.axis.legend(**self.legend_kwargs)
  
          return
docs: Make the horizon plot.