Method concatMapMaybe

src/main/java/io/reactivex/rxjava3/core/Single.java:2759–2764

Returns a Maybe that is based on applying a specified function to the item emitted by the current Single, where that function returns a MaybeSource. <img width="640" height="254" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/Single.concatMapMaybe.p

(@NonNull Function<? super T, ? extends MaybeSource<? extends R>> mapper)

     * @since 3.0.0
     */
    @CheckReturnValue
    @NonNull
    @SchedulerSupport(SchedulerSupport.NONE)
    public final <@NonNull R> Maybe<R> concatMapMaybe(@NonNull Function<? super T, ? extends MaybeSource<? extends R>> mapper) {
        return flatMapMaybe(mapper);
    }

    /**
     * Returns a {@link Flowable} that emits the item emitted by the current {@code Single}, then the item emitted by the