src/main/java/io/reactivex/Flowable.java
@CheckReturnValue
    @NonNull
    @BackpressureSupport(BackpressureKind.PASS_THROUGH)
    @SchedulerSupport(SchedulerSupport.NONE)
    public final Flowable<T> takeUntil(Predicate<? super T> stopPredicate) {
        ObjectHelper.requireNonNull(stopPredicate, "stopPredicate is null");
        return RxJavaPlugins.onAssembly(new FlowableTakeUntilPredicate<T>(this, stopPredicate));
    }
@CheckReturnValue
    @NonNull
    @BackpressureSupport(BackpressureKind.PASS_THROUGH)
    @SchedulerSupport(SchedulerSupport.NONE)
    public final Flowable<T> takeUntil(Predicate<? super T> stopPredicate) {
        ObjectHelper.requireNonNull(stopPredicate, "stopPredicate is null");
        return RxJavaPlugins.onAssembly(new FlowableTakeUntilPredicate<T>(this, stopPredicate));
    }
Returns a Flowable that emits items emitted by the source Publisher, checks the specified predicate
for each item, and then completes when the condition is satisfied.
<p>
<img width="640" height="305" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/takeUntil.p.png" alt="">
<p>
The difference between this operator and {@link #takeWhile(Predicate)} is that here, the condition is
evaluated <em>after</em> the item is emitted.

<dl>
<dt><b>Backpressure:</b></dt>
<dd>The operator is a pass-through for backpressure; the backpressure behavior is determined by the upstream
source and the downstream consumer.</dd>
<dt><b>Scheduler:</b></dt>
<dd>{@code takeUntil} does not operate by default on a particular {@link Scheduler}.</dd>
</dl>

@param stopPredicate
a function that evaluates an item emitted by the source Publisher and returns a Boolean
@return a Flowable that first emits items emitted by the source Publisher, checks the specified
condition after each item, and then completes when the condition is satisfied.
@see <a href="http://reactivex.io/documentation/operators/takeuntil.html">ReactiveX operators documentation: TakeUntil</a>
@see Flowable#takeWhile(Predicate)
@since 1.1.0