code: @BackpressureSupport(BackpressureKind.FULL)
      @CheckReturnValue
      @SchedulerSupport(SchedulerSupport.NONE)
      public static <T> Flowable<T> concatArrayEager(SingleSource<? extends T>... sources) {
          return Flowable.fromArray(sources).concatMapEager(SingleInternalHelper.<T>toFlowable());
      }
docs: Concatenates a sequence of SingleSource eagerly into a single stream of values.
  <p>
  Eager concatenation means that once a subscriber subscribes, this operator subscribes to all of the
  source SingleSources. The operator buffers the value emitted by these SingleSources and then drains them
  in order, each one after the previous one completes.
  <dl>
  <dt><b>Backpressure:</b></dt>
  <dd>The operator honors backpressure from downstream.</dd>
  <dt><b>Scheduler:</b></dt>
  <dd>This method does not operate by default on a particular {@link Scheduler}.</dd>
  </dl>
  @param <T> the value type
  @param sources a sequence of Single that need to be eagerly concatenated
  @return the new Flowable instance with the specified concatenation behavior