@SuppressWarnings({ "unchecked" })
    @CheckReturnValue
    @SchedulerSupport(SchedulerSupport.NONE)
    public static <T> Observable<T> concatArrayDelayError(ObservableSource<? extends T>... sources) {
        if (sources.length == 0) {
            return empty();
        } else
        if (sources.length == 1) {
            return (Observable<T>)wrap(sources[0]);
        }
        return concatDelayError(fromArray(sources));
    }