    /**
     *  Ignores all elements in an observable sequence leaving only the termination messages.
     * @returns {Observable} An empty observable sequence that signals termination, successful or exceptional, of the source sequence.    
     */
    observableProto.ignoreElements = function () {
        var source = this;
        return new AnonymousObservable(function (observer) {
            return source.subscribe(noop, observer.onError.bind(observer), observer.onCompleted.bind(observer));
        });
    };
