Create from list of `fnames` in `path` with `label_func`.

def from_name_func(cls, path:PathOrStr, fnames:FilePathList, label_func:Callable, valid_pct:float=0.2, **kwargs):
        "Create from list of `fnames` in `path` with `label_func`."
        src = ImageList(fnames, path=path).split_by_rand_pct(valid_pct)
        return cls.create_from_ll(src.label_from_func(label_func), **kwargs)