docs: def _add_scope_decorations(self, block, start, end):
          """
          Show a scope decoration on the editor widget
  
          :param start: Start line
          :param end: End line
          """
          try:
              parent = FoldScope(block).parent()
          except ValueError:
              parent = None
          if TextBlockHelper.is_fold_trigger(block):
              base_color = self._get_scope_highlight_color()
              factor_step = 5
              if base_color.lightness() < 128:
                  factor_step = 10
                  factor = 70
              else:
                  factor = 100
              while parent:
                  # highlight parent scope
                  parent_start, parent_end = parent.get_range()
                  self._add_scope_deco(
                      start, end + 1, parent_start, parent_end,
                      base_color, factor)
                  # next parent scope
                  start = parent_start
                  end = parent_end
                  parent = parent.parent()
                  factor += factor_step
              # global scope
              parent_start = 0
              parent_end = self.editor.document().blockCount()
              self._add_scope_deco(
                  start, end + 1, parent_start, parent_end, base_color,
                  factor + factor_step)
          else:
              self._clear_scope_decos()