For loop in another for loop

mainsubjects:
    -
         title: title
         text: test
         links:
            -
                title: test
                link: http://www.test.com
            -
                title: test
                link: http://www.test.com
    -
         title: title
         text: test
         links:
            -
                title: test
                link: http://www.test.com
            -
                title: test
                link: http://www.test.com

   <div class="card-group transp">
  {% for mainsubject in page.header.mainsubjects %}
  <div class="card transp">
    <div class="card-block">
      <h4 class="card-title">{{ mainsubject.title }}</h4>
      <p class="card-text">{{ mainsubject.text }}</p>
      <ul class="list-group list-group-flush">
        {% for link in mainsubject.links %}
        <li class="list-group-item transp"><a href="{{ link.title }}" class="card-link">{{ link.title }}</a></li>
        {% endfor %}
      </ul>
    </div>
  </div>
  {% endfor %}
</div>