title: Haystack, SearchQuerySet().filter is not returning anything. ( django + elastic search)
body: <p>my code looks like following. here SearchQuerySet().filer is not returning anything.</p>
  
  <blockquote>
    <p>search_indexes.py</p>
  </blockquote>
  
  <pre><code>class sample_index(indexes.SearchIndex, indexes.Indexable):
      text = indexes.CharField(document=True, use_template=True)
      books = indexes.CharField(model_attr='books')
      search_tags = indexes.MultiValueField()
  
      def prepere_tags(self, obj):
          return [tag.tag for tag in obj.seacrh_tags.all()]
  
      def get_model(self):
          return sample
  
      def index_queryset(self, using=None):
          return self.get_model().objects
  
      def load_all_queryset(self):
          return sample.objects.all().select_related()
  </code></pre>
  
  <blockquote>
  <pre><code>model.py
  </code></pre>
  </blockquote>
  
  <pre><code>class tags(models.Model):    
      tag = models.CharField(max_length=4, unique=True, db_index=True)
  
      def __unicode__(self):
          return unicode(self.tag)
  
  class sample(models.Model):
  
  books = models.CharField(db_index=True, max_length=256, null=False)
  search_tags = models.ManyToManyField(tags, db_index=True)
  
  def __unicode__(self):
      return unicode(self.md5sum)
  </code></pre>
  
  <blockquote>
    <p>view.py</p>
  </blockquote>
  
  <pre><code>def search_h(request):
  
      search_string = request.GET.get('search_string', '')
      values = []
  
      sqs = SearchQuerySet().filter(search_tags=search_string)
  
      values = [a.object for a in sqs[0:10]]
  
      return render(request, "search/indexes/app/test.html", {'values': values})
  </code></pre>
  
  <blockquote>
    <p>sample_text.txt</p>
  </blockquote>
  
  <pre><code>{{ object.text }}
  {% for tag in object.search_tags.all %}
  {{ tag.tag }}
  {% endfor %}
  </code></pre>
  
  <p>Here values is a empty list. even sqs is coming as empty. Any idea what am i missing here.</p>