src/main/java/io/reactivex/Maybe.java
@CheckReturnValue
    @NonNull
    @SchedulerSupport(SchedulerSupport.NONE)
    public static <T> Maybe<T> unsafeCreate(MaybeSource<T> onSubscribe) {
        if (onSubscribe instanceof Maybe) {
            throw new IllegalArgumentException("unsafeCreate(Maybe) should be upgraded");
        }
        ObjectHelper.requireNonNull(onSubscribe, "onSubscribe is null");
        return RxJavaPlugins.onAssembly(new MaybeUnsafeCreate<T>(onSubscribe));
    }
@CheckReturnValue
    @NonNull
    @SchedulerSupport(SchedulerSupport.NONE)
    public static <T> Maybe<T> unsafeCreate(MaybeSource<T> onSubscribe) {
        if (onSubscribe instanceof Maybe) {
            throw new IllegalArgumentException("unsafeCreate(Maybe) should be upgraded");
        }
        ObjectHelper.requireNonNull(onSubscribe, "onSubscribe is null");
        return RxJavaPlugins.onAssembly(new MaybeUnsafeCreate<T>(onSubscribe));
    }
<strong>Advanced use only:</strong> creates a Maybe instance without
any safeguards by using a callback that is called with a MaybeObserver.
<dl>
<dt><b>Scheduler:</b></dt>
<dd>{@code unsafeCreate} does not operate by default on a particular {@link Scheduler}.</dd>
</dl>
@param <T> the value type
@param onSubscribe the function that is called with the subscribing MaybeObserver
@return the new Maybe instance