title: Making SDWebImage appear with fade in animation
body: <p>I would like to set an animation, when an image is loaded.</p>
  
  <p>I use <code>SDWebImage</code> to load pictures:</p>
  
  <pre><code>if let photoUrlString = post?.photoUrl {
           let photoUrl = URL(string: photoUrlString)
           picImg.sd_setImage(with: photoUrl)
  }
  </code></pre>
  
  <p>How can I code a "fade in" effect when the picture is loaded? </p>