custom tags for Template

[mathiasbc]

I am trying to write a custom tool on the Unlayer Dashboard. I need the toll to use a custom tag I have defined in my Django environment and I need Unlayer to spit HTML for it so my email engine can inject the right content. I need something like:

{% custom_items count={{count_property}} as items %}
{% for item in items %}
  <li>{{item.name}}</li>
{% endfor %}

But obviously custom_items is not a valid tag in Nunjucks and I don't think I can assign with as items. Is there anything that can be done to achieve this ?