code: @SuppressWarnings({ "unchecked", "rawtypes" })
      @BackpressureSupport(BackpressureKind.FULL)
      @CheckReturnValue
      @SchedulerSupport(SchedulerSupport.NONE)
      public static <T> Flowable<T> concatDelayError(Iterable<? extends MaybeSource<? extends T>> sources) {
          ObjectHelper.requireNonNull(sources, "sources is null");
          return Flowable.fromIterable(sources).concatMapDelayError((Function)MaybeToPublisher.instance());
      }
docs: Concatenates the Iterable sequence of MaybeSources into a single sequence by subscribing to each MaybeSource,
  one after the other, one at a time and delays any errors till the all inner MaybeSources terminate.
  <p>
  <img width="640" height="469" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/Maybe.concatDelayError.i.png" alt="">
  <dl>
  <dt><b>Backpressure:</b></dt>
  <dd>The operator honors backpressure from downstream.</dd>
  <dt><b>Scheduler:</b></dt>
  <dd>{@code concatDelayError} does not operate by default on a particular {@link Scheduler}.</dd>
  </dl>
  
  @param <T> the common element base type
  @param sources the Iterable sequence of MaybeSources
  @return the new Flowable with the concatenating behavior