code: def next_valid_batch(self, batch_size):
          
          start = self.index_in_valid_epoch
          if self.index_in_valid_epoch + batch_size > self.num_valid_images:
              batch_size = 1
          self.index_in_valid_epoch += batch_size
          end = self.index_in_valid_epoch
          return self.valid_labels[start:end], self.img_norm(self.valid_images[start:end]), end, batch_size
docs: Return the next batch of examples from validiation data set
          :param batch_size: int, size of image batch returned
          :return train_labels: list, of labels
          :return images: list, of images