/**

* Returns an {@code Observable} that concatenate each item emitted by the current {@code Observable} with the values in an

* {@link Iterable} corresponding to that item that is generated by a selector.

* <p>

* <img width="640" height="275" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/concatMapIterable.o.png" alt="">

*

* <dl>

* <dt><b>Scheduler:</b></dt>

* <dd>{@code concatMapIterable} does not operate by default on a particular {@link Scheduler}.</dd>

* </dl>

*

* @param <U>

* the type of item emitted by the resulting {@code Observable}

* @param mapper

* a function that returns an {@code Iterable} sequence of values for when given an item emitted by the

* current {@code Observable}

* @param bufferSize

* the number of elements expected from the current {@code Observable} to be buffered

* @return an {@code Observable} that emits the results of concatenating the items emitted by the current {@code Observable} with

* the values in the {@code Iterable}s corresponding to those items

* @throws NullPointerException if {@code mapper} is {@code null}

* @throws IllegalArgumentException if {@code bufferSize} is non-positive

* @see <a href="https://reactivex.io/documentation/operators/flatmap.html">ReactiveX operators documentation: FlatMap</a>

*/

@CheckReturnValue

@SchedulerSupport(SchedulerSupport.NONE)

@NonNull

public final <U> Observable<U> concatMapIterable(@NonNull Function<? super T, ? extends Iterable<? extends U>> mapper, int bufferSize) {

Objects.requireNonNull(mapper, "mapper is null");

ObjectHelper.verifyPositive(bufferSize, "bufferSize");

return concatMap(ObservableInternalHelper.flatMapIntoIterable(mapper), bufferSize);

}

}, 1)