Method wrap

src/main/java/io/reactivex/rxjava3/core/Observable.java:4432–4441

Wraps an ObservableSource into an Observable if not already an Observable. Scheduler: wrap does not operate by default on a particular Scheduler. @param the value type @param source the ObservableSource insta

(@NonNull ObservableSource<T> source)

     * @throws NullPointerException if {@code source} is {@code null}
     */
    @CheckReturnValue
    @SchedulerSupport(SchedulerSupport.NONE)
    @NonNull
    public static <@NonNull T> Observable<T> wrap(@NonNull ObservableSource<T> source) {
        Objects.requireNonNull(source, "source is null");
        if (source instanceof Observable) {
            return RxJavaPlugins.onAssembly((Observable<T>)source);
        }
        return RxJavaPlugins.onAssembly(new ObservableFromUnsafeSource<>(source));
    }

    /**
     * Returns an {@code Observable} that emits the results of a specified combiner function applied to combinations of