docs/_includes/subitems.html
{% if include.items %}
<ul class="dropdown-menu">
{% for item_hash in include.items %}
{% assign item = item_hash[1] %}
{% assign subitems = item.items %}
<li{% if subitems %} class="submenu"{% endif %}>{% include menu_item.html item=item %}</li>
{% endfor %}
</ul>
{% endif %}