def _read(self):
        """get two list, each list contains two elements: name and nd.array value"""
        _, data_img_name, label_img_name = self.f.readline().strip('\n').split("\t")
        data = {}
        label = {}
        data[self.data_name], label[self.label_name] = self._read_img(data_img_name, label_img_name)
        return list(data.items()), list(label.items())