set url value into iframe src

backstage/templates/editor.html

@@ -1,5 +1,5 @@
 {% extends "layout.html" %}
-{% block content %}
+{% block main %}
   <div class="ui segment">
     <div class="ui two column very relaxed grid">
       <div class="column">
@@ -16,10 +16,10 @@
         <script type="text/javascript" src="{{url_for('static', filename='js/editor.js')}}"></script>
       </div>
       <div class="column">
-        <iframe src='http://localhost:1313/collection/doll_and_drum_set/' width="100%" height="100%"></iframe>
+        <iframe src='http://localhost:1313{{ url }}/' width="100%" height="100%"></iframe>
       </div>
     </div>
     <div class="ui vertical divider">
     </div>
   </div>
-{% endblock content %}
+{% endblock main %}