title: How to use lean() with mongoose and bluebird?
body: <p>I'm kind of new with Promises and Bluebird. <br>
  I was trying to make a query using Mongoose and Bluebird. <br>
  I've already promisified mongoose and added the <strong>Async</strong> suffix to the find function as you can see in the code below  </p>
  
  <pre><code>function getLocations() {
    var query = {}
    var selection = {
      coordinates: 1,
      geoFence: 1
    }
    return MyLocation.findAsync(query, selection).lean()
  }  
  </code></pre>
  
  <p>I've tested it and it works without the <code>lean()</code> function, but when I use the <code>lean()</code> function the code breaks with the following message</p>
  
  <p><strong>TypeError: MyLocation.findAsync(...).lean is not a function</strong><br>
  Can you tell me what I'm doing wrong?</p>