title: Filter through a related model django
body: <p>How can I generate a query_set through a related model?</p>
  
  <p>For example, how can I do this:</p>
  
  <pre><code>UserProfile.objects.filter(user.is_active=True) # Can't use user.is_active to filter
  </code></pre>
  
  <p>Trivial question, trivial answer. But I'll keep it here for posterity's sake.</p>