src/main/java/io/reactivex/Maybe.java
@BackpressureSupport(BackpressureKind.FULL)
    @CheckReturnValue
    @SchedulerSupport(SchedulerSupport.NONE)
    public static <T> Flowable<T> merge(Publisher<? extends MaybeSource<? extends T>> sources) {
        return merge(sources, Integer.MAX_VALUE);
    }
@BackpressureSupport(BackpressureKind.FULL)
    @CheckReturnValue
    @SchedulerSupport(SchedulerSupport.NONE)
    public static <T> Flowable<T> merge(Publisher<? extends MaybeSource<? extends T>> sources) {
        return merge(sources, Integer.MAX_VALUE);
    }
Merges a Flowable sequence of MaybeSource instances into a single Flowable sequence,
running all MaybeSources at once.
<dl>
<dt><b>Backpressure:</b></dt>
<dd>The operator honors backpressure from downstream.</dd>
<dt><b>Scheduler:</b></dt>
<dd>{@code merge} does not operate by default on a particular {@link Scheduler}.</dd>
<dt><b>Error handling:</b></dt>
<dd>If any of the source {@code MaybeSource}s signal a {@code Throwable} via {@code onError}, the resulting
{@code Flowable} terminates with that {@code Throwable} and all other source {@code MaybeSource}s are disposed.
If more than one {@code MaybeSource} signals an error, the resulting {@code Flowable} may terminate with the
first one's error or, depending on the concurrency of the sources, may terminate with a
{@code CompositeException} containing two or more of the various error signals.
{@code Throwable}s that didn't make into the composite will be sent (individually) to the global error handler via
{@link RxJavaPlugins#onError(Throwable)} method as {@code UndeliverableException} errors. Similarly, {@code Throwable}s
signaled by source(s) after the returned {@code Flowable} has been cancelled or terminated with a
(composite) error will be sent to the same global error handler.
Use {@link #mergeDelayError(Publisher)} to merge sources and terminate only when all source {@code MaybeSource}s
have completed or failed with an error.
</dd>
</dl>
@param <T> the common and resulting value type
@param sources the Flowable sequence of MaybeSource sources
@return the new Flowable instance
@see #mergeDelayError(Publisher)