consistency with other layers.
*   Some files in `tensorflow/python/training` have been moved to
    `tensorflow/python/tracking` and `tensorflow/python/checkpoint`. Please
    update your imports accordingly, the old files will be removed in Release
    2.11.
*   `tf.keras.optimizers.experimental.Optimizer` will graduate in Release 2.11,
    which means `tf.keras.optimizers.Optimizer` will be an alias of