docs: def toggle_fold_trigger(self, block):
          """
          Toggle a fold trigger block (expand or collapse it).
  
          :param block: The QTextBlock to expand/collapse
          """
          if not TextBlockHelper.is_fold_trigger(block):
              return
          region = FoldScope(block)
          if region.collapsed:
              region.unfold()
              if self._mouse_over_line is not None:
                  self._add_scope_decorations(
                      region._trigger, *region.get_range())
          else:
              region.fold()
              self._clear_scope_decos()
          self._refresh_editor_and_scrollbars()
          self.trigger_state_changed.emit(region._trigger, region.collapsed)