src/main/java/io/reactivex/Observable.java
@CheckReturnValue
    @SchedulerSupport(SchedulerSupport.NONE)
    public final Maybe<T> lastElement() {
        return RxJavaPlugins.onAssembly(new ObservableLastMaybe<T>(this));
    }
@CheckReturnValue
    @SchedulerSupport(SchedulerSupport.NONE)
    public final Maybe<T> lastElement() {
        return RxJavaPlugins.onAssembly(new ObservableLastMaybe<T>(this));
    }
Returns a Maybe that emits the last item emitted by this Observable or
completes if this Observable is empty.
<p>
<img width="640" height="305" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/lastElement.png" alt="">
<dl>
<dt><b>Scheduler:</b></dt>
<dd>{@code lastElement} does not operate by default on a particular {@link Scheduler}.</dd>
</dl>

@return a Maybe that emits the last item from the source ObservableSource or notifies observers of an
error
@see <a href="http://reactivex.io/documentation/operators/last.html">ReactiveX operators documentation: Last</a>