<nav class="bd-links">
  {% if include.category_id %}
    {% assign category_id = include.category_id %}
    {% assign category_links = site.data.links.categories[category_id] %}
  {% else %}
    {% assign category_links = site.data.links.categories %}
  {% endif %}

  {% for link_id in category_links %}
    {% if include.category_id %}
      {% assign link = site.data.links.by_id[link_id] %}
    {% else %}
      {% assign thingy = link_id[0] %}
      {% assign link = site.data.links.by_id[thingy] %}
    {%