src/main/java/io/reactivex/Flowable.java
@CheckReturnValue
    @BackpressureSupport(BackpressureKind.UNBOUNDED_IN)
    @SchedulerSupport(SchedulerSupport.NONE)
    public final Observable<T> toObservable() {
        return RxJavaPlugins.onAssembly(new ObservableFromPublisher<T>(this));
    }
@CheckReturnValue
    @BackpressureSupport(BackpressureKind.UNBOUNDED_IN)
    @SchedulerSupport(SchedulerSupport.NONE)
    public final Observable<T> toObservable() {
        return RxJavaPlugins.onAssembly(new ObservableFromPublisher<T>(this));
    }
Converts the current Flowable into a non-backpressured {@link Observable}.
<dl>
<dt><b>Backpressure:</b></dt>
<dd>Observables don't support backpressure thus the current Flowable is consumed in an unbounded
manner (by requesting Long.MAX_VALUE).</dd>
<dt><b>Scheduler:</b></dt>
<dd>{@code toObservable} does not operate by default on a particular {@link Scheduler}.</dd>
</dl>
@return the new Observable instance
@since 2.0