Fix for newer Keras versions

[progmars]

I got an error:
AttributeError: module 'keras.backend' has no attribute 'image_dim_ordering'

If you want to support newer Keras, then according to this:
keras-team/keras#12649
the method has be renamed to image_data_format.

[Rockzzzz-221]

instead of that you can use image_data_format()