@class NSObject; @protocol OS_dispatch_queue; @interface _NUObservation : NSObject @property (readonly, weak, nonatomic) id observer; @property (readonly, nonatomic) long long key; @property (readonly, nonatomic) NSObject<OS_dispatch_queue> *queue; @property (readonly, nonatomic) id /* block */ block; - (id)init; - (void).cxx_destruct; - (id)initWithObserver:(id)a0 key:(long long)a1 queue:(id)a2 block:(id /* block */)a3; - (void)notifyWithBlock:(id /* block */)a0; @end