code: def whiteness_index(self):
          
          mean_vis = (self.blue + self.green + self.red) / 3
  
          blue_absdiff = np.absolute(self._divide_zero(self.blue - mean_vis, mean_vis))
          green_absdiff = np.absolute(self._divide_zero(self.green - mean_vis, mean_vis))
          red_absdiff = np.absolute(self._divide_zero(self.red - mean_vis, mean_vis))
  
          return blue_absdiff + green_absdiff + red_absdiff
docs: Index of "Whiteness" based on visible bands.
          Parameters
          ----------
  
          Output
          ------
          ndarray:
              whiteness index