How could I change the parent background css from a menu?

I'm using boostrap. I would like to change the "my-parent" menu with CSS, when it is with the class "collapse.in":

<nav class="col-xs-12 col-md-2 pull-left meu-parent">
    <div class="menu-dropdown-test"> <!-- collapse.in só aparece quando ele está com o collapse ativo, acontece logo aqui abaixo:  -->
        <div class="navbar-collapse navbar-menubuilder collapse in" aria-expanded="true" style="">
            <ul class="nav navbar-nav navbar-left menu-webapp-v2">
                <li><a href="/webapp/home"><i class="item-leitura"></i><span>Leitura</span></a></li>
                <li><a href="/webapp/conquistas"><i class="item-conquistas"></i><span>Conquistas</span></a></li>
                <li><a href="/webapp/a-producao-textual"><i class="item-producao-textual"></i><span>Produção textual</span></a></li>
                <li class="nav-close"><a href="/webapp/sair"><i class="item-sair"></i>Sair</a></li>
            </ul>
        </div>
    </div>
</nav>

Is there any way to make collapse.in's css work for a parent > parent I need to change the background to a black with opacity 0.6 when the menu dropdown is open (with collapse.in).