src/main/java/io/reactivex/Observable.java
@CheckReturnValue
    @SchedulerSupport(SchedulerSupport.NONE)
    public final Observable<T> take(long time, TimeUnit unit) {
        return takeUntil(timer(time, unit));
    }
@CheckReturnValue
    @SchedulerSupport(SchedulerSupport.NONE)
    public final Observable<T> take(long time, TimeUnit unit) {
        return takeUntil(timer(time, unit));
    }
Returns an Observable that emits those items emitted by source ObservableSource before a specified time runs
out.
<p>
If time runs out before the {@code Observable} completes normally, the {@code onComplete} event will be
signaled on the default {@code computation} {@link Scheduler}.
<p>
<img width="640" height="305" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/take.t.png" alt="">
<dl>
<dt><b>Scheduler:</b></dt>
<dd>This version of {@code take} operates by default on the {@code computation} {@link Scheduler}.</dd>
</dl>

@param time
the length of the time window
@param unit
the time unit of {@code time}
@return an Observable that emits those items emitted by the source ObservableSource before the time runs out
@see <a href="http://reactivex.io/documentation/operators/take.html">ReactiveX operators documentation: Take</a>