Nested navigation bar using Python and Jinja based on a JSON object

nav.py

{% set active_page = active_page|default('') -%}
<nav role="navigation">
    <ul>
        {%- for nav_link in my_nav recursive -%}
            <li><a class="nav-link{% if nav_link.id == active_page %} nav-active{% endif %}" href="{{ nav_link.url|e }}">{{ nav_link.title|e }}</a>
            {%- if nav_link.children -%}
                <ul>{{ loop(nav_link.children) }}</ul>
            {%- endif %}
            </li>
        {%- endfor %}
    </ul>
</nav>