title: django: How to get objects from a ContentType instance
body: <p>I want to get a queryset of objects from a ContentType instance and then be able to filter them. From the doc, it is possible to <code>get()</code> an object using:</p>
  
  <pre><code>ct.get_object_for_this_type(**kwargs)
  </code></pre>
  
  <p>How can I make a similar <code>filter()</code> for that instance?</p>