Create normalize/denormalize func using `mean` and `std`, can specify `do_y` and `device`.

def normalize_funcs(mean:FloatTensor, std:FloatTensor, do_x:bool=True, do_y:bool=False)->Tuple[Callable,Callable]:
    "Create normalize/denormalize func using `mean` and `std`, can specify `do_y` and `device`."
    mean,std = tensor(mean),tensor(std)
    return (partial(_normalize_batch, mean=mean, std=std, do_x=do_x, do_y=do_y),
            partial(denormalize,      mean=mean, std=std, do_x=do_x))