Label `self.items` with `labels`.

def _label_from_list(self, labels:Iterator, label_cls:Callable=None, from_item_lists:bool=False, **kwargs)->'LabelList':
        "Label `self.items` with `labels`."
        if not from_item_lists:
            raise Exception("Your data isn't split, if you don't want a validation set, please use `split_none`.")
        labels = array(labels, dtype=object)
        label_cls = self.get_label_cls(labels, label_cls=label_cls, **kwargs)
        y = label_cls(labels, path=self.path, **kwargs)
        res = self._label_list(x=self, y=y)
        return res