def build_densenet():
densenet = DenseNet121(weights=‘imagenet’, include_top=False)
input = Input(shape=(SIZE, SIZE, N_ch))
x = Conv2D(3, (3, 3), padding='same')(input)
x = densenet(x)
x = GlobalAveragePooling2D()(x)
x = BatchNormalization()(x)
x = Dropout(0.5)(x)
x = Dense(256, activation='relu')(x)
x = BatchNormalization()(x)
x = Dropout(0.5)(x)
# multi output
output = Dense(2,activation = 'softmax', name='root')(x)
# model
model = Model(input,output)