title: PyMongo $inc having issues
body: <p>When trying to use $inc I get a Syntax error stating that $set is wrong. My query is as follow:</p>
  
  <pre><code>mongo_db.campaign.update({'_id': str(campaign_id)}, { $inc: { 'item': 1 } }):
  </code></pre>
  
  <p>I've looked at the mongo documentation (<a href="http://docs.mongodb.org/manual/reference/operator/inc/" rel="noreferrer">http://docs.mongodb.org/manual/reference/operator/inc/</a>) and other examples on SO but I can't find what's wrong. Any suggestions?</p>
  
  <p>Thanks!</p>