{% macro list(items, class) %}
<ul class="{{class}}">

   {# Iterating over each direct items #}
   {% for item in items %}
   <li>
      <a href="">{{item.name}}</a>

      {# If an item has children #}
      {% if item.children %}
         {# Re-import the macro #}
         {% import _self as recursive %}
         {# And use it to iterate over item's children #}
         {{ recursive.list(item.children) }}
      {% endif %}
   </li>
   {% endfor %}
</ul>
{% endmacro %}


{# Nav Being the variable passed to the template #}
{% if nav %}
   {# importing the macro created earlier #}
   {% import _self as tree %}

   {# using macro {nameOfImport}.{nameOfMethod}(variable) #}
   {{ tree.list(nav.children) }}
{% endif %}