@interface RLMNotificationToken : NSObject
A token which is returned from methods which subscribe to changes to a Realm.
Change subscriptions in Realm return an
which can be used to unsubscribe from the changes. You must store a strong
reference to the token for as long as you want to continue to receive notifications.
When you wish to stop, call the
-invalidate method. Notifications are also stopped if
the token is deallocated.