code: @SuppressWarnings({ "unchecked", "rawtypes" })
      @CheckReturnValue
      @BackpressureSupport(BackpressureKind.FULL)
      @SchedulerSupport(SchedulerSupport.NONE)
      public static <T> Flowable<T> concatDelayError(Iterable<? extends Publisher<? extends T>> sources) {
          ObjectHelper.requireNonNull(sources, "sources is null");
          return fromIterable(sources).concatMapDelayError((Function)Functions.identity());
      }
docs: Concatenates the Iterable sequence of Publishers into a single sequence by subscribing to each Publisher,
  one after the other, one at a time and delays any errors till the all inner Publishers terminate.
  
  <dl>
  <dt><b>Backpressure:</b></dt>
  <dd>The operator honors backpressure from downstream. Both the outer and inner {@code Publisher}
  sources are expected to honor backpressure as well. If the outer violates this, a
  {@code MissingBackpressureException} is signaled. If any of the inner {@code Publisher}s violates
  this, it <em>may</em> throw an {@code IllegalStateException} when an inner {@code Publisher} completes.</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 Publishers
  @return the new Publisher with the concatenating behavior