title: Ambiguous use of 'observeSingleEvent(of: with:)
body: <p>I am trying to get some users' profile pictures. Here is the code I am starting with:</p>
  
  <pre><code>databaseRef.child("Users").queryOrderedByKey().observeSingleEvent(of: .childAdded) { (snapshot) in
  
  }
  </code></pre>
  
  <p>I am trying to follow a Swift 2 tutorial; however, I am using Swift 3. I have tried to adjust the code already, but I have not been successful as I get the following error</p>
  
  <blockquote>
    <p>Ambiguous use of 'observeSingleEvent(of:with:)'</p>
  </blockquote>
  
  <p>This error is on the first line. How can I resolve this? Thanks!</p>