What does {$ … $} stand for in django templates?

I have a Django App with an AngularJS (1.5.8) frontend and stumbled across a notation in the templates that I don’t understand. I also can’t find any explanation in the Django or AngularJS docs.

<div class="form-label">
   {$ ... $}
</div>

I know, that one can use {{ ... }} for variables, {% ... %} for tags or {# ... #} for comments. But what is {$ ... $} for?

Any ideas?

Source: AngularJS