title: Serializing django-mptt trees in Tastypie
body: <p>How do I serialize <code>django-mptt</code> trees in <code>Tastypie</code>?</p>
  
  <p>I want to use <code>django-mptt</code>'s <code>cache_tree_children()</code>. I've tried applying in different Tastypie hooks, but it throws an error.</p>