Cannot load IsDarkMode

I have been unable to load the IsDarkMode function, is there good reason why we cannot load it or should I be doing it somehow differently ?

IsDarkMode_fp = (RBBoolean (*)())REALLoadFrameworkMethod(“IsDarkMode() as Boolean”);

tried also

IsDarkMode_fp = (RBBoolean (*)())REALLoadFrameworkMethod(“REALbasic.IsDarkMode() as Boolean”);

Thanks