Can't get code on page 137 to work

[JeremyWhittaker]

I'm trying to write the code from page 137 and I'm getting an error. I have no idea how to troubleshoot or perhaps it's just a simple typo. I've gone over the code multiple times and can't figure it out.

https://colab.research.google.com/drive/1CZXpt7xman0PL6lU9-HoL1oIphPHeADy?usp=sharing

Epoch 1/3
---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
<ipython-input-11-da7c14b3ed65> in <module>()
      1 if __name__ == "__main__":
----> 2   run(0)
      3   run(1)
      4   run(2)
      5   run(3)

10 frames
/usr/local/lib/python3.7/dist-packages/tensorflow/python/framework/func_graph.py in wrapper(*args, **kwargs)
    992           except Exception as e:  # pylint:disable=broad-except
    993             if hasattr(e, "ag_error_metadata"):
--> 994               raise e.ag_error_metadata.to_exception(e)
    995             else:
    996               raise

ValueError: in user code:

    /usr/local/lib/python3.7/dist-packages/keras/engine/training.py:853 train_function  *
        return step_function(self, iterator)
    /usr/local/lib/python3.7/dist-packages/keras/engine/training.py:842 step_function  **
        outputs = model.distribute_strategy.run(run_step, args=(data,))
    /usr/local/lib/python3.7/dist-packages/tensorflow/python/distribute/distribute_lib.py:1286 run
        return self._extended.call_for_each_replica(fn, args=args, kwargs=kwargs)
    /usr/local/lib/python3.7/dist-packages/tensorflow/python/distribute/distribute_lib.py:2849 call_for_each_replica
        return self._call_for_each_replica(fn, args, kwargs)
    /usr/local/lib/python3.7/dist-packages/tensorflow/python/distribute/distribute_lib.py:3632 _call_for_each_replica
        return fn(*args, **kwargs)
    /usr/local/lib/python3.7/dist-packages/keras/engine/training.py:835 run_step  **
        outputs = model.train_step(data)
    /usr/local/lib/python3.7/dist-packages/keras/engine/training.py:787 train_step
        y_pred = self(x, training=True)
    /usr/local/lib/python3.7/dist-packages/keras/engine/base_layer.py:1020 __call__
        input_spec.assert_input_compatibility(self.input_spec, inputs, self.name)
    /usr/local/lib/python3.7/dist-packages/keras/engine/input_spec.py:202 assert_input_compatibility
        ' input tensors. Inputs received: ' + str(inputs))

    ValueError: Layer model_4 expects 1 input(s), but it received 23 input tensors. Inputs received: [<tf.Tensor 'ExpandDims:0' shape=(None, 1) dtype=int64>, <tf.Tensor 'ExpandDims_1:0' shape=(None, 1) dtype=int64>, <tf.Tensor 'ExpandDims_2:0' shape=(None, 1) dtype=int64>, <tf.Tensor 'ExpandDims_3:0' shape=(None, 1) dtype=int64>, <tf.Tensor 'ExpandDims_4:0' shape=(None, 1) dtype=int64>, <tf.Tensor 'ExpandDims_5:0' shape=(None, 1) dtype=int64>, <tf.Tensor 'ExpandDims_6:0' shape=(None, 1) dtype=int64>, <tf.Tensor 'ExpandDims_7:0' shape=(None, 1) dtype=int64>, <tf.Tensor 'ExpandDims_8:0' shape=(None, 1) dtype=int64>, <tf.Tensor 'ExpandDims_9:0' shape=(None, 1) dtype=int64>, <tf.Tensor 'ExpandDims_10:0' shape=(None, 1) dtype=int64>, <tf.Tensor 'ExpandDims_11:0' shape=(None, 1) dtype=int64>, <tf.Tensor 'ExpandDims_12:0' shape=(None, 1) dtype=int64>, <tf.Tensor 'ExpandDims_13:0' shape=(None, 1) dtype=int64>, <tf.Tensor 'ExpandDims_14:0' shape=(None, 1) dtype=int64>, <tf.Tensor 'ExpandDims_15:0' shape=(None, 1) dtype=int64>, <tf.Tensor 'ExpandDims_16:0' shape=(None, 1) dtype=int64>, <tf.Tensor 'ExpandDims_17:0' shape=(None, 1) dtype=int64>, <tf.Tensor 'ExpandDims_18:0' shape=(None, 1) dtype=int64>, <tf.Tensor 'ExpandDims_19:0' shape=(None, 1) dtype=int64>, <tf.Tensor 'ExpandDims_20:0' shape=(None, 1) dtype=int64>, <tf.Tensor 'ExpandDims_21:0' shape=(None, 1) dtype=int64>, <tf.Tensor 'ExpandDims_22:0' shape=(None, 1) dtype=int64>]