执行下面代码段,对其输出结果描述错误的是_______。import tensorflow as tfimport numpy as npimport matplotlib.pyplot as pltmnist = tf.keras.datasets.mnist(train_x, train_y), (test_x, test_y) = mnist.load_data()for i in range(8): num = np.random.randint(1,60000) plt.subplot(2, 4, i+1) plt.axis("off") plt.imshow(train_x[num], cmap='gray')plt.title(train_y[num])plt.show()