title: AttributeError: 'RelatedManager' object has no attribute 'remove'
body: <p>Somewhere in my code it says</p>
  
  <pre><code>publisher.publisherperson_set.remove(email__in=pp_remove_set)
  </code></pre>
  
  <p>Upon executing this, I got</p>
  
  <blockquote>
    <p>AttributeError: 'RelatedManager' object has no attribute 'remove'</p>
  </blockquote>
  
  <p>And indeed: I looked at <code>dir(publisher.publisherperson_set)</code> and it had plenty of operations (including <code>add</code>), but not <code>remove</code>.</p>
  
  <p>Under which circumstances is this possible?</p>