src/main/java/io/reactivex/Observable.java
@CheckReturnValue
    @SchedulerSupport(SchedulerSupport.CUSTOM)
    public final Observable<T> takeLast(long count, long time, TimeUnit unit, Scheduler scheduler, boolean delayError, int bufferSize) {
        ObjectHelper.requireNonNull(unit, "unit is null");
        ObjectHelper.requireNonNull(scheduler, "scheduler is null");
        ObjectHelper.verifyPositive(bufferSize, "bufferSize");
        if (count < 0) {
            throw new IndexOutOfBoundsException("count >= 0 required but it was " + count);
        }
        return RxJavaPlugins.onAssembly(new ObservableTakeLastTimed<T>(this, count, time, unit, scheduler, bufferSize, delayError));
    }
@CheckReturnValue
    @SchedulerSupport(SchedulerSupport.CUSTOM)
    public final Observable<T> takeLast(long count, long time, TimeUnit unit, Scheduler scheduler, boolean delayError, int bufferSize) {
        ObjectHelper.requireNonNull(unit, "unit is null");
        ObjectHelper.requireNonNull(scheduler, "scheduler is null");
        ObjectHelper.verifyPositive(bufferSize, "bufferSize");
        if (count < 0) {
            throw new IndexOutOfBoundsException("count >= 0 required but it was " + count);
        }
        return RxJavaPlugins.onAssembly(new ObservableTakeLastTimed<T>(this, count, time, unit, scheduler, bufferSize, delayError));
    }
Returns an Observable that emits at most a specified number of items from the source ObservableSource that were
emitted in a specified window of time before the ObservableSource completed, where the timing information is
provided by a given Scheduler.
<p>
<img width="640" height="310" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/takeLast.tns.png" alt="">
<dl>
<dt><b>Scheduler:</b></dt>
<dd>You specify which {@link Scheduler} this operator will use for tracking the current time</dd>
</dl>

@param count
the maximum number of items to emit
@param time
the length of the time window
@param unit
the time unit of {@code time}
@param scheduler
the {@link Scheduler} that provides the timestamps for the observed items
@param delayError
if true, an exception signalled by the current Observable is delayed until the regular elements are consumed
by the downstream; if false, an exception is immediately signalled and all regular elements dropped
@param bufferSize
the hint about how many elements to expect to be last
@return an Observable that emits at most {@code count} items from the source ObservableSource that were emitted
in a specified window of time before the ObservableSource completed, where the timing information is
provided by the given {@code scheduler}
@throws IndexOutOfBoundsException
if {@code count} is less than zero
@see <a href="http://reactivex.io/documentation/operators/takelast.html">ReactiveX operators documentation: TakeLast</a>