*   Extend `tf.strings.split` to support inputs with any rank.
    *   Added `tf.random.binomial`.
    *   Added `key` and `skip` methods to `random.experimental.Generator`.
    *   Extend `tf.function` with basic support for CompositeTensors arguments
        (such as `SparseTensor` and `RaggedTensor`).
    *   `parallel_for.pfor`: add converters for Softmax, LogSoftmax, IsNaN, All,
        Any, and MatrixSetDiag.