{% if collection_name %}
<form class="navbar-form navbar-left" method="GET" action="{% url 'search_indexes:collection_haystack_search' collection_name %}" role="search">
  {% else %}
<form class="navbar-form navbar-left" method="GET" action="{% url 'search_indexes:haystack_search' %}" role="search">
{% endif %}
  <div class="form-group">
    <input name="q" type="text" class="form-control" placeholder="Trouver ...">
    <select name="model_type" class="form-control">
      <option value="images">Images</option>
      <option value="annotations">Annotations</option>
    </select>
    <button type="submit" class="btn btn-default"><i class="fa fa-search" aria-hidden="true"></i></button>
  </div>
</form>