title: Django and extra field in query
body: <p>I have a my query in Django that returns a list of user.</p>
  
  <p>Now, for every returned user, I would to add an extra field: I need to know if the user is already friend of the current user. </p>
  
  <p>I not understand if I have to use .annotate or extra() or other. I'm very confused.</p>
  
  <p>I also tried this code but not work:</p>
  
  <pre><code>query = query.annotate(are_friends=Count(Q(user__friends=user)))
  </code></pre>
  
  <p>I obtain this error: <code>'Q' object has no attribute 'split'</code></p>