src/main/java/io/reactivex/Completable.java
@CheckReturnValue
    @NonNull
    @SchedulerSupport(SchedulerSupport.NONE)
    public static Completable wrap(CompletableSource source) {
        ObjectHelper.requireNonNull(source, "source is null");
        if (source instanceof Completable) {
            return RxJavaPlugins.onAssembly((Completable)source);
        }
        return RxJavaPlugins.onAssembly(new CompletableFromUnsafeSource(source));
    }
@CheckReturnValue
    @NonNull
    @SchedulerSupport(SchedulerSupport.NONE)
    public static Completable wrap(CompletableSource source) {
        ObjectHelper.requireNonNull(source, "source is null");
        if (source instanceof Completable) {
            return RxJavaPlugins.onAssembly((Completable)source);
        }
        return RxJavaPlugins.onAssembly(new CompletableFromUnsafeSource(source));
    }
Wraps the given CompletableSource into a Completable
if not already Completable.
<p>
<img width="640" height="354" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/Completable.wrap.png" alt="">
<dl>
<dt><b>Scheduler:</b></dt>
<dd>{@code wrap} does not operate by default on a particular {@link Scheduler}.</dd>
</dl>
@param source the source to wrap
@return the source or its wrapper Completable
@throws NullPointerException if source is null