*   `tf.keras`
    *   Export `depthwise_conv2d` in `tf.keras.backend`.
    *   In Keras Layers and Models, Variables in `trainable_weights`,
        `non_trainable_weights`, and `weights` are explicitly deduplicated.
    *   Keras `model.load_weights` now accepts `skip_mismatch` as an argument.
        This was available in external Keras, and has now been copied over to
        `tf.keras`.