title: django: cannot import name SimpleListFilter
body: <p>I have the code form <a href="https://docs.djangoproject.com/en/dev/ref/contrib/admin/#django.contrib.admin.ModelAdmin.list_filter" rel="nofollow">django docs</a>, but this will output an error.</p>
  
  <blockquote>
    <p>ImportError: cannot import name SimpleListFilter</p>
  </blockquote>
  
  <p>I am using django 1.3</p>
  
  <p>Anyone knows what's problem with this import?</p>
  
  <p>Thanks!</p>