public function render_core_availability_multiple_messages(
            core_availability_multiple_messages $renderable) {
        // Get initial message.
        $out = get_string('list_' . ($renderable->root ? 'root_' : '') .
                ($renderable->andoperator ? 'and' : 'or') . ($renderable->treehidden ? '_hidden' : ''),
                'availability');

        // Make the list.
        $out .= html_writer::start_tag('ul');
        foreach ($renderable->items as $item) {
            if (is_string($item)) {
                $str = $item;
            } else {
                $str = $this->render($item);
            }
            $out .= html_writer::tag('li', $str);
        }
        $out .= html_writer::end_tag('ul');
        return $out;
    }