如何在Tensorflow 2.0中冻结隐藏层中的权重来重新训练DNN

import tensorflow as tf
from tensorflow.keras import models

pretrained_model = tf.keras.applications.MobileNetV2(weights='imagenet', include_top=False)

pretrained_model.trainable = False

model = models.Sequential()
model.add(pretrained_model)
model.add(tf.keras.layers.Flatten())
model.add(tf.keras.layers.Dense(10, activation='softmax'))

model.compile(optimizer='adam', loss='categorical_crossentropy', metrics=['accuracy'])
model.fit(train_images, train_labels, epochs=10, validation_data=(val_images, val_labels))