Chapter 7. Step 13 gives a error

[zoldaten]

c:\python64\lib\site-packages\tensorflow\python\keras\engine\training_utils.py in standardize_single_array(x)
79 elif tensor_util.is_tensor(x):
80 return x
---> 81 elif x.ndim == 1:
82 x = np.expand_dims(x, 1)
83 return x

AttributeError: 'NumpyArrayIterator' object has no attribute 'ndim'