title: Remove duplicates in Django ORM -- multiple rows
body: <p>I have a model that has four fields. How do I remove duplicate objects from my database?</p>
  
  <p>Daniel Roseman's answer to <a href="https://stackoverflow.com/questions/5877306/remove-duplicates-in-a-django-query">this question</a> seems appropriate, but I'm not sure how to extend this to situation where there are four fields to compare per object.</p>
  
  <p>Thanks,</p>
  
  <p>W.</p>