Method reduce

src/main/java/io/reactivex/rxjava3/core/Flowable.java:13505–13512

Returns a Maybe that applies a specified accumulator function to the first item emitted by the current Flowable, then feeds the result of that function along with the second item emitted by the current Flowable into the same function, and so on until all items have been emitt

(@NonNull BiFunction<T, T, T> reducer)

     * @see <a href="http://en.wikipedia.org/wiki/Fold_(higher-order_function)">Wikipedia: Fold (higher-order function)</a>
     */
    @CheckReturnValue
    @NonNull
    @BackpressureSupport(BackpressureKind.UNBOUNDED_IN)
    @SchedulerSupport(SchedulerSupport.NONE)
    public final Maybe<T> reduce(@NonNull BiFunction<T, T, T> reducer) {
        Objects.requireNonNull(reducer, "reducer is null");
        return RxJavaPlugins.onAssembly(new FlowableReduceMaybe<>(this, reducer));
    }

    /**
     * Returns a {@link Single} that applies a specified accumulator function to the first item emitted by the current