WP nav menu + Bootstrap, add role="menu" to UL

Question

For one of my projects I'm trying to add a nav_menu to my WP theme. It should work as a quick menu (sidebar). The only problem remaining: How do I add a role="menu" to the < ul >?

    <?php
        wp_nav_menu( array(
            'menu'              => 'menu',
            'theme_location'    => 'menu',
            'depth'             => 0,
            'container'         => '',
            'menu_class'        => 'dropdown-menu',
            'fallback_cb'       => 'wp_bootstrap_navwalker::fallback',
            'walker'            => new wp_bootstrap_navwalker())
        );
    ?>  

I'm looking for the output <ul class="dropdown-menu" role="menu"> anyone ?

Answer 1

[Update] Solution found:

I was looking for 'items_wrap' => '<ul id="%1$s" class="%2$s" role="menu" >%3$s</ul>'

    <?php
        wp_nav_menu( array(
            'menu'              => 'menu',
            'theme_location'    => 'menu',
            'items_wrap' => '<ul id="%1$s" class="%2$s" role="menu" >%3$s</ul>',
            'depth'             => 0,
            'container'         => '',
            'menu_class'        => 'dropdown-menu',
            'fallback_cb'       => 'wp_bootstrap_navwalker::fallback',
            'walker'            => new wp_bootstrap_navwalker())
        );
    ?>