title: module 'keras.layers.normalization' has no attribute 'BatchNormalizationBase'
body: <p>when i run this code</p>
  <pre><code> import os
   from autokeras import 
   StructuredDataClassifier
   import stellargraph as sg
   from stellargraph.mapper import 
   FullBatchNodeGenerator
   from tensorflow.keras import layers, 
   optimizers, losses, metrics, Model
   from sklearn import preprocessing, 
   model_selection
   from IPython.display import display, HTML
   import matplotlib.pyplot as plt
   %matplotlib inline
  </code></pre>
  <p>i have this error</p>
  <pre><code> AttributeError: module 'keras.layers.normalization' has no attribute 'BatchNormalizationBase'
  </code></pre>
  <p>Knowing that this code has been run many times without any problems</p>