event: https://connpass.com/event/138112/
source: https://gist.github.com/omochi/4ddc82cd94d3e1ea1c5cd348ba7733da
When I wrote this slides, I didn't know about `tf.function`.
https://www.tensorflow.org/beta/tutorials/eager/tf_function
So explanation about TensorFlow 2.X in presentation might not be fair.