src/main/java/io/reactivex/Observable.java
@CheckReturnValue
    @SchedulerSupport(SchedulerSupport.NONE)
    public final Single<Boolean> any(Predicate<? super T> predicate) {
        ObjectHelper.requireNonNull(predicate, "predicate is null");
        return RxJavaPlugins.onAssembly(new ObservableAnySingle<T>(this, predicate));
    }
@CheckReturnValue
    @SchedulerSupport(SchedulerSupport.NONE)
    public final Single<Boolean> any(Predicate<? super T> predicate) {
        ObjectHelper.requireNonNull(predicate, "predicate is null");
        return RxJavaPlugins.onAssembly(new ObservableAnySingle<T>(this, predicate));
    }
Returns a Single that emits {@code true} if any item emitted by the source ObservableSource satisfies a
specified condition, otherwise {@code false}. <em>Note:</em> this always emits {@code false} if the
source ObservableSource is empty.
<p>
<img width="640" height="320" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/any.2.png" alt="">
<p>
In Rx.Net this is the {@code any} Observer but we renamed it in RxJava to better match Java naming
idioms.
<dl>
<dt><b>Scheduler:</b></dt>
<dd>{@code any} does not operate by default on a particular {@link Scheduler}.</dd>
</dl>

@param predicate
the condition to test items emitted by the source ObservableSource
@return a Single that emits a Boolean that indicates whether any item emitted by the source
ObservableSource satisfies the {@code predicate}
@see <a href="http://reactivex.io/documentation/operators/contains.html">ReactiveX operators documentation: Contains</a>