在书面代码下面，

from __future__ import print_function
import keras
from keras.datasets import mnist
from keras.models import Sequential
from keras.layers import Dense, Dropout, Flatten
from tensorflow.keras.layers import Conv2D
from tensorflow.keras.layers import MaxPooling2D
from keras.layers import backend as k

batch_size = 128
num_classes = 10
epochs = 12

及以下问题，

---------------------------------------------------------------------------
ImportError                               Traceback (most recent call last)
<ipython-input-1-d1183f2cea73> in <module>
      8 from tensorflow.keras.layers import Conv2D
      9 from tensorflow.keras.layers import MaxPooling2D
---> 10 from keras.layers import backend as k
     11 
     12 

ImportError: cannot import name 'backend'

需要帮助解决此问题
注意：我使用的是Python 3.6.0。