src/main/java/io/reactivex/Flowable.java
@CheckReturnValue
    @NonNull
    @BackpressureSupport(BackpressureKind.FULL)
    @SchedulerSupport(SchedulerSupport.NONE)
    public final Flowable<T> mergeWith(@NonNull SingleSource<? extends T> other) {
        ObjectHelper.requireNonNull(other, "other is null");
        return RxJavaPlugins.onAssembly(new FlowableMergeWithSingle<T>(this, other));
    }
@CheckReturnValue
    @NonNull
    @BackpressureSupport(BackpressureKind.FULL)
    @SchedulerSupport(SchedulerSupport.NONE)
    public final Flowable<T> mergeWith(@NonNull SingleSource<? extends T> other) {
        ObjectHelper.requireNonNull(other, "other is null");
        return RxJavaPlugins.onAssembly(new FlowableMergeWithSingle<T>(this, other));
    }
Merges the sequence of items of this Flowable with the success value of the other SingleSource.
<p>
<img width="640" height="380" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/merge.png" alt="">
<p>
The success value of the other {@code SingleSource} can get interleaved at any point of this
{@code Flowable} sequence.
<dl>
<dt><b>Backpressure:</b></dt>
<dd>The operator honors backpressure from downstream and ensures the success item from the
{@code SingleSource} is emitted only when there is a downstream demand.</dd>
<dt><b>Scheduler:</b></dt>
<dd>{@code mergeWith} does not operate by default on a particular {@link Scheduler}.</dd>
</dl>
<p>History: 2.1.10 - experimental
@param other the {@code SingleSource} whose success value to merge with
@return the new Flowable instance
@since 2.2