 
 extension AudioItem {
     /// The list of properties that is observed through KVO.
-    private static var KVOProperties: [String] {
+    private static var ap_KVOProperties: [String] {
         return ["artist", "title", "album", "trackCount", "trackNumber", "artworkImage"]
     }
 }

        }

        //Observing AudioItem's property
        for keyPath in AudioItem.KVOProperties {
            item.addObserver(self, forKeyPath: keyPath, options: .New, context: nil)
        }


        }

        //Unobserving AudioItem's property
        for keyPath in AudioItem.ap_KVOProperties {
            item.removeObserver(self, forKeyPath: keyPath)
        }

