src/main/java/io/reactivex/Observable.java
@CheckReturnValue
    @SchedulerSupport(SchedulerSupport.NONE)
    public final Completable ignoreElements() {
        return RxJavaPlugins.onAssembly(new ObservableIgnoreElementsCompletable<T>(this));
    }
@CheckReturnValue
    @SchedulerSupport(SchedulerSupport.NONE)
    public final Completable ignoreElements() {
        return RxJavaPlugins.onAssembly(new ObservableIgnoreElementsCompletable<T>(this));
    }
Ignores all items emitted by the source ObservableSource and only calls {@code onComplete} or {@code onError}.
<p>
<img width="640" height="305" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/ignoreElements.2.png" alt="">
<dl>
<dt><b>Scheduler:</b></dt>
<dd>{@code ignoreElements} does not operate by default on a particular {@link Scheduler}.</dd>
</dl>

@return the new Completable instance
@see <a href="http://reactivex.io/documentation/operators/ignoreelements.html">ReactiveX operators documentation: IgnoreElements</a>