title: Unhandled rejection MongoError: The dollar ($) prefixed field '$inc' in '$inc' is not valid for storage
body: <p>I am getting following error while i am trying to increment a field by a specified value in mongodb using $inc </p>
  
  <p>"Unhandled rejection MongoError: The dollar ($) prefixed field '$inc' in '$inc' is not valid for storage."</p>
  
  <p>Below is my code</p>
  
  <pre><code>APILog.update({ apiId: 1 }, {$inc:{"dataCount":10}}); 
  </code></pre>
  
  <p>Thanks in advance</p>