title: Attribute error on keras on tensorflow
body: <p>While using <code>Tensorflow v.1.0.1</code> and <code>Keras 2.0</code> and running this code:</p>
  
  <pre><code>from keras import backend as K
  if K.image_data_format() == 'channels_first':
  input_shape = (1, img_width, img_height)
  </code></pre>
  
  <p>I'm getting the following error:</p>
  
  <blockquote>
    <p>AttributeError: module 'keras.backend' has no attribute
    'image_data_format'</p>
  </blockquote>
  
  <p>How can I solve this?</p>