{% macro make_toc( toc ) -%}
<nav>
    <ul>
        {% for toc_item in toc -%}
        <li><a href="{{ toc_item.url }}">{{ toc_item.title}}</a></li>
        {% for toc_item in toc_item.children -%}
        <li><a href="{{ toc_item.url }}">{{ toc_item.title }}</a></li>
        {%- endfor %}
        {%- endfor %}
    </ul>
</nav>
{%- endmacro -%}