title: Django related key of the same model
body: <p>I'm working on a feature for an app much like a Twitter Retweet.</p>
  
  <p>In the model for <code>Item</code>, I want to add a related field for <code>reposted_from</code> that will reference another <code>Item</code>. I dont think I use <code>ForeignKey</code> for this, since it's the same Model, but what do I use instead?</p>