templates/nav-bar.html

<nav class="navbar navbar-expand-lg navbar-dark bg-dark mb-2">
    <!-- <a class="navbar-brand" href="#">Navbar</a> -->
    <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarSupportedContent"
        aria-controls="navbarSupportedContent" aria-expanded="false" aria-label="Toggle navigation">
        <span class="navbar-toggler-icon"></span>
    </button>

    <div class="collapse navbar-collapse" id="navbarSupportedContent">
        <ul class="navbar-nav mr-auto">
            <li class="nav-item">
                <a class="nav-link" href="{%url 'ml_app:home'%}">Home</a>
            </li>
            <!-- <li class="nav-item">
                <a class="nav-link" href="{%url 'ml_app:about'%}">About</a>
            </li>
            <li class="nav-item">
                <a class="nav-link" href="#">GitHub</a>
            </li> -->
        </ul>
    </div>
</nav>