code: def _shade_remaining_missing(self):
          
          # Sanity check.
          if not self.shade_missing:
              return
  
          # Run through each missing label left in the current page and shade it.
          missing = self._used.get(self.page_count, set())
          for position in missing:
              self._position = position
              self._shade_missing_label()
docs: Helper method to shade any missing labels remaining on the current
          page. Not intended for external use.
  
          Note that this will modify the internal _position attribute and should
          therefore only be used once all the 'real' labels have been drawn.