`tf.nn.safe_embedding_lookup_sparse`, `tf.nn.sampled_softmax` and
        `tf.nn.nce_loss`. hyperparameter are ignored.
*   Performance
    *   Improve performance of GPU cumsum/cumprod by up to 300x.
    *   Added support for weight decay in most TPU embedding optimizers,
        including AdamW and MomentumW.
*   TensorFlow 2.0 Development
    *   Add a command line tool to convert to TF2.0, tf_upgrade_v2