Method error

src/main/java/io/reactivex/rxjava3/core/Observable.java:1839–1845

Returns an Observable that invokes an Observer's Observer#onError onError method when the Observer subscribes to it. Schedu

(@NonNull Supplier<? extends @NonNull Throwable> supplier)

     * @see <a href="http://reactivex.io/documentation/operators/empty-never-throw.html">ReactiveX operators documentation: Throw</a>
     */
    @CheckReturnValue
    @NonNull
    @SchedulerSupport(SchedulerSupport.NONE)
    public static <@NonNull T> Observable<T> error(@NonNull Supplier<? extends @NonNull Throwable> supplier) {
        Objects.requireNonNull(supplier, "supplier is null");
        return RxJavaPlugins.onAssembly(new ObservableError<>(supplier));
    }

    /**
     * Returns an {@code Observable} that invokes an {@link Observer}'s {@link Observer#onError onError} method when the