title: How to use completion block using SDWebImage in Swift 3.0?
body: <p>Am using <a href="https://github.com/rs/SDWebImage" rel="noreferrer">SDWebImage</a> to download image. I want to do further operation if image is downloaded successfully.</p>
  
  <pre><code>cell.appIcon.sd_setImage(with: url, placeholderImage: UIImage.init(named: "App-Default"), completed: {(image: UIImage!, error: NSError!, cacheType: SDImageCacheType, imageURL: URL!) -&gt; Void in
        // Perform operation. 
  })
  </code></pre>
  
  <p>But I am getting error: </p>
  
  <blockquote>
    <p>Cannot convert value of type '(UIImage!, NSError!, SDImageCacheType, URL!) -> Void' to expected argument type 'SDExternalCompletionBlock?'</p>
  </blockquote>