Plot MINST数据集图像返回AttributeError：'dict‘对象没有属性'train’

{
    'train': {
        'images': ...,
        'labels': ...
    },
    'test': {
        'images': ...,
        'labels': ...
    }
}

import tensorflow as tf
import matplotlib.pyplot as plt

# 加载 MINST 数据集
mnist = tf.keras.datasets.mnist
(train_images, train_labels), (test_images, test_labels) = mnist.load_data()

# 显示训练集中的前几张图像
plt.figure(figsize=(10, 10))
for i in range(25):
    plt.subplot(5, 5, i+1)
    plt.xticks([])
    plt.yticks([])
    plt.grid(False)
    plt.imshow(train_images[i], cmap=plt.cm.binary)
    plt.xlabel(train_labels[i])
plt.show()