ظهور الخطأ 'AttributeError: module 'keras.engine' has no attribute 'Network أثناء محاولة استخدام keras.engine.Network

أقوم بالعمل على موديل بسيط في keras ولكن لا أعرف ما الخطأ في keras.engine.Network:

import keras
from keras import backend 
from keras.models import Sequential
from keras import layers
from keras.datasets import mnist
model = Sequential()
model.add(layers.Flatten())
model.add(layers.Dense(512, activation='relu', input_shape=( 28*28,)))
model.add(layers.Dense(10, activation='softmax'))
model.compile(optimizer='Adam', loss='sparse_categorical_crossentropy', metrics=['accuracy'])
def init(model):
     session = backend.get_session()
     for layer in model.layers: 
        if isinstance(layer,keras.engine.Network):
             init(layer)
init(model)
---------------------------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)

<ipython-input-9-487617649ac0> in <module>()
     16         if isinstance(layer,keras.engine.Network):
     17              init(layer)
---> 18 init(model)

<ipython-input-9-487617649ac0> in init(model)
     14      session = backend.get_session()
     15      for layer in model.layers:
---> 16         if isinstance(layer,keras.engine.Network):
     17              init(layer)
     18 init(model)

AttributeError: module 'keras.engine' has no attribute 'Network'