如何在Keras中使用densenet

from keras.applications.densenet import DenseNet121
from keras.models import Model
from keras.layers import Dense, GlobalAveragePooling2D

base_model = DenseNet121(weights='imagenet', include_top=False)

x = base_model.output
x = GlobalAveragePooling2D()(x)
x = Dense(1024, activation='relu')(x)
predictions = Dense(num_classes, activation='softmax')(x)

model = Model(inputs=base_model.input, outputs=predictions)

model.compile(optimizer='adam', loss='categorical_crossentropy', metrics=['accuracy'])
model.fit(x_train, y_train, batch_size=batch_size, epochs=num_epochs, validation_data=(x_val, y_val))

predictions = model.predict(x_test)