public void PhotosAddTagTest()
        {
            string photoId = "4499284951";
            string tag     = "testx";

            var w = new AsyncSubject <FlickrResult <NoResponse> >();

            AuthInstance.PhotosAddTagsAsync(photoId, tag, r => { w.OnNext(r); w.OnCompleted(); });

            var result = w.Next().First();
        }