tensorflow2 keras 简单的手写体识别训练

    import tensorflow as tf
    from tensorflow.keras.layers import Dense, Flatten
    from tensorflow.keras import Model
    import os
    mnist = tf.keras.datasets.mnist
    (x_train, y_train), (x_test, y_test) = mnist.load_data()
    x_train, x_test = x_train / 255.0, x_test / 255.0
    
    
    class MnistModel(Model):
    def __init__(self):
        super(MnistModel, self).__init__()
        self.flatten = Flatten()
        self.d1 = Dense(128, activation='relu')
        self.d2 = Dense(10, activation='softmax')
    
    def call(self, x