title: django : get object from foreign key
body: <p>Suppose following model class,</p>
  
  <blockquote>
  <pre><code> class Bookmark(models.Model):   
       owner = models.ForeignKey(UserProfile,related_name='bookmarkOwner')
       parent = models.ForeignKey(UserProfile,related_name='bookmarkParent')
       sitter = models.ForeignKey(UserProfile,related_name='bookmarkSitter')
  </code></pre>
  </blockquote>
  
  <p>How can I get <code>sitter</code> objects from <code>owner</code> Objects?</p>
  
  <pre><code>user = UserProfile.objects.get(pk=1)
  
  UserProfile.objects.filter(bookmarkOwner=user)
  </code></pre>
  
  <p>returns empty <code>tuple</code>, and I cannot specify <code>sitter</code> variable.</p>