<nav class="breadcrumb" aria-label="breadcrumbs">
    {% for part in config.content %}
    <ul>
      {% if part.id == current_part %}
      <li><a href="{{config.url_prefix}}/{{part.id}}/index.html">{{part.index.content.title}}</a></li>
      {% if part.chapters %}
      
      {% for chapter in part.chapters %}
      
      {% if current_chapter == chapter.id %}
            <li><a href="{{config.url_prefix}}/{{part.id}}/{{ chapter.id }}/index.html">{{ chapter.index.content.title }}</a></li>
            {% for doc in chapter.documents %}
              {% if current_doc == doc.id %}
              <li><a href="{{config.url_prefix}}/{{part.id}}/{{ chapter.id }}/{{doc.id}}.html">{{doc.content.title}}</a></li>
              {% endif %}
            {% endfor %}
      {% endif %}
        
        {% endfor %}

      {% endif %}
      {% endif %}
      </ul>
    {% endfor %}
   
  </nav>