code: def _draw_fold_region_background(self, block, painter):
          
          r = FoldScope(block)
          th = TextHelper(self.editor)
          start, end = r.get_range(ignore_blank_lines=True)
          if start > 0:
              top = th.line_pos_from_number(start)
          else:
              top = 0
          bottom = th.line_pos_from_number(end + 1)
          h = bottom - top
          if h == 0:
              h = self.sizeHint().height()
          w = self.sizeHint().width()
          self._draw_rect(QRectF(0, top, w, h), painter)
docs: Draw the fold region when the mouse is over and non collapsed
          indicator.
  
          :param top: Top position
          :param block: Current block.
          :param painter: QPainter