internal static TObserver Observe <T, TObserver>(this IPInvokeObservable <T> @this, TObserver observer) where TObserver : IPinvokeObserver <T> { if (@this == null) { throw new ArgumentNullException(nameof(@this)); } if (observer == null) { throw new ArgumentNullException(nameof(observer)); } @this.Subscribe(observer); return(observer); }