title: UICollectionView insert/delete animations
body: <p>I have to do some updates on my custom UICollectionView after inserting and/or deleting some cells. But I would like to do the updates after the animations (triggered by inserting and/or deleting) are done.</p>
  
  <p>How can I tell when UICollectionView insert/delete animations?</p>
  
  <p>Thanks!</p>
  
  <p>PS: In Swift.</p>