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)