    <div class="container">
            <a class="navbar-brand mr-1 mb-1 mt-0" href="../">Bootstrap 4</a>
            <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#collapsingNavbar">
                <span class="navbar-toggler-icon"></span>
            </button>
            <div class="navbar-collapse collapse justify-content-center" id="collapsingNavbar">
                <ul class="navbar-nav">
                    <li class="nav-item dropdown">
                        <a