pythonで見分けさせたい

pythonで畳み込みニューラルネットワークを使って学習させたいです
そこで以下の記事とコードをとってきてやっています。
記事
 コード
ですが、以下のエラーが出てきて実行できません

Using TensorFlow backend.
x_train shape: (50000, 32, 32, 3)
50000 train samples
10000 test samples
WARNING:tensorflow:From /Users/takabatomoki/.pyenv/versions/3.7.1/lib/python3.7/site-packages/tensorflow/python/framework/op_def_library.py:263: colocate_with (from tensorflow.python.framework.ops) is deprecated and will be removed in a future version.
Instructions for updating:
Colocations handled automatically by placer.
WARNING:tensorflow:From /Users/takabatomoki/.pyenv/versions/3.7.1/lib/python3.7/site-packages/keras/backend/tensorflow_backend.py:3445: calling dropout (from tensorflow.python.ops.nn_ops) with keep_prob is deprecated and will be removed in a future version.
Instructions for updating:
Please use `rate` instead of `keep_prob`. Rate should be set to `rate = 1 - keep_prob`.
Using real-time data augmentation.
WARNING:tensorflow:From /Users/takabatomoki/.pyenv/versions/3.7.1/lib/python3.7/site-packages/tensorflow/python/ops/math_ops.py:3066: to_int32 (from tensorflow.python.ops.math_ops) is deprecated and will be removed in a future version.
Instructions for updating:
Use tf.cast instead.
Traceback (most recent call last):
  File "cifar10_cnn.py", line 119, in <module>
    workers=4)
  File "/Users/takabatomoki/.pyenv/versions/3.7.1/lib/python3.7/site-packages/keras/legacy/interfaces.py", line 91, in wrapper
    return func(*args, **kwargs)
  File "/Users/takabatomoki/.pyenv/versions/3.7.1/lib/python3.7/site-packages/keras/engine/training.py", line 1418, in fit_generator
    initial_epoch=initial_epoch)
  File "/Users/takabatomoki/.pyenv/versions/3.7.1/lib/python3.7/site-packages/keras/engine/training_generator.py", line 55, in fit_generator
    raise ValueError('`steps_per_epoch=None` is only valid for a'
ValueError: `steps_per_epoch=None` is only valid for a generator based on the `keras.utils.Sequence` class. Please specify `steps_per_epoch` or use the `keras.utils.Sequence` class.