src/main/java/io/reactivex/Maybe.java
@BackpressureSupport(BackpressureKind.FULL)
    @CheckReturnValue
    @NonNull
    @SchedulerSupport(SchedulerSupport.NONE)
    public final <U> Flowable<U> flattenAsFlowable(final Function<? super T, ? extends Iterable<? extends U>> mapper) {
        ObjectHelper.requireNonNull(mapper, "mapper is null");
        return RxJavaPlugins.onAssembly(new MaybeFlatMapIterableFlowable<T, U>(this, mapper));
    }
@BackpressureSupport(BackpressureKind.FULL)
    @CheckReturnValue
    @NonNull
    @SchedulerSupport(SchedulerSupport.NONE)
    public final <U> Flowable<U> flattenAsFlowable(final Function<? super T, ? extends Iterable<? extends U>> mapper) {
        ObjectHelper.requireNonNull(mapper, "mapper is null");
        return RxJavaPlugins.onAssembly(new MaybeFlatMapIterableFlowable<T, U>(this, mapper));
    }
@ BackpressureSupport ( BackpressureKind . FULL ) @ CheckReturnValue @ NonNull @ SchedulerSupport ( SchedulerSupport . NONE ) public final < U > Flowable < U > flattenAsFlowable ( final Function < ? super T , ? extends Iterable < ? extends U > > mapper ) { ObjectHelper . requireNonNull ( mapper , "mapper is null" ) ; return RxJavaPlugins . onAssembly ( new MaybeFlatMapIterableFlowable < T , U > ( this , mapper ) ) ; }
Maps the success value of the upstream {@link Maybe} into an {@link Iterable} and emits its items as a
{@link Flowable} sequence.
<p>
<img width="640" height="373" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/flattenAsFlowable.png" alt="">
<dl>
<dt><b>Backpressure:</b></dt>
<dd>The operator honors backpressure from downstream.</dd>
<dt><b>Scheduler:</b></dt>
<dd>{@code flattenAsFlowable} does not operate by default on a particular {@link Scheduler}.</dd>
</dl>

@param <U>
the type of item emitted by the resulting Iterable
@param mapper
a function that returns an Iterable sequence of values for when given an item emitted by the
source Maybe
@return the new Flowable instance
@see <a href="http://reactivex.io/documentation/operators/flatmap.html">ReactiveX operators documentation: FlatMap</a>
Maps the success value of the upstream { @link Maybe } into an { @link Iterable } and emits its items as a { @link Flowable } sequence . <p > <img width = 640 height = 373 src = https : // raw . github . com / wiki / ReactiveX / RxJava / images / rx - operators / flattenAsFlowable . png alt = > <dl > <dt > <b > Backpressure : < / b > < / dt > <dd > The operator honors backpressure from downstream . < / dd > <dt > <b > Scheduler : < / b > < / dt > <dd > { @code flattenAsFlowable } does not operate by default on a particular { @link Scheduler } . < / dd > < / dl >