src/main/java/io/reactivex/Observable.java
@CheckReturnValue
    @SchedulerSupport(SchedulerSupport.NONE)
    public static <T> Single<Boolean> sequenceEqual(ObservableSource<? extends T> source1, ObservableSource<? extends T> source2,
            BiPredicate<? super T, ? super T> isEqual) {
        return sequenceEqual(source1, source2, isEqual, bufferSize());
    }
@CheckReturnValue
    @SchedulerSupport(SchedulerSupport.NONE)
    public static <T> Single<Boolean> sequenceEqual(ObservableSource<? extends T> source1, ObservableSource<? extends T> source2,
            BiPredicate<? super T, ? super T> isEqual) {
        return sequenceEqual(source1, source2, isEqual, bufferSize());
    }
Returns a Single that emits a Boolean value that indicates whether two ObservableSource sequences are the
same by comparing the items emitted by each ObservableSource pairwise based on the results of a specified
equality function.
<p>
<img width="640" height="380" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/sequenceEqual.2.png" alt="">
<dl>
<dt><b>Scheduler:</b></dt>
<dd>{@code sequenceEqual} does not operate by default on a particular {@link Scheduler}.</dd>
</dl>

@param source1
the first ObservableSource to compare
@param source2
the second ObservableSource to compare
@param isEqual
a function used to compare items emitted by each ObservableSource
@param <T>
the type of items emitted by each ObservableSource
@return a Single that emits a Boolean value that indicates whether the two ObservableSource two sequences
are the same according to the specified function
@see <a href="http://reactivex.io/documentation/operators/sequenceequal.html">ReactiveX operators documentation: SequenceEqual</a>