code: def split_data(self, train_images, train_labels):
          
          valid_images = train_images[:self.num_valid_images]
          valid_labels = train_labels[:self.num_valid_images]
          train_images = train_images[self.num_valid_images:]
          train_labels = train_labels[self.num_valid_images:]
          return train_images, train_labels, valid_images, valid_labels
docs: :param train_images: numpy array (image_dim, image_dim, num_images)
          :param train_labels: numpy array (labels)
          :return: train_images, train_labels, valid_images, valid_labels