【Swift】MPMediaPickerController を使って、itunesのアートワーク（画像）を取得する

func mediaPicker(_ mediaPicker: MPMediaPickerController, didPickMediaItems mediaItemCollection: MPMediaItemCollection) {
let item:MPMediaItem = mediaItemCollection.items[0]
if(item.artwork != nil){
let imgSize:CGSize = CGSize(width: (item.artwork?.bounds.size.width)!, height: (item.artwork?.bounds.size.height)!)
let image: UIImage? = item.artwork?.image(at: imgSize)
}
}