code: def _highlight_block(self, block):
          
          scope = FoldScope(block)
          if (self._current_scope is None or
                  self._current_scope.get_range() != scope.get_range()):
              self._current_scope = scope
              self._clear_scope_decos()
              # highlight current scope with darker or lighter color
              start, end = scope.get_range()
              if not TextBlockHelper.is_collapsed(block):
                  self._decorate_block(start, end)
docs: Highlights the current fold scope.
  
          :param block: Block that starts the current fold scope.