three hyperbolical Lines representing the Terminus of the Shadow of one
of the Knives, the dark Line between the first and second Fringes of
that Shadow, and the dark Line between the second and third Fringes of
the same Shadow; _xip_, _ykq_, and _zlr_, three other hyperbolical Lines
representing the Terminus of the Shadow of the other Knife, the dark
Line between the first and second Fringes of that Shadow, and the dark

        via `tf.GradientTape.stop_recording`.
    *   Updated documentation, introductory notebooks.
*   `tf.keras`:
    *   Move Keras code out of _impl folder and remove API files.
    *   `tf.keras.Model.save_weights` now saves in TensorFlow format by default.
    *   Enable dataset iterators to be passed to `tf.keras.Model` training/eval
        methods.