code: def __draw_leaf_density(self):
          
          leafs = self.__directory.get_leafs()
          density_scale = leafs[-1].get_density()
  
          if density_scale == 0.0: density_scale = 1.0
  
          for block in leafs:
              alpha = 0.8 * block.get_density() / density_scale
              self.__draw_block(block, alpha)
docs: !
          @brief Display densities by filling blocks by appropriate colors.