treated as tensors, so if you still want them to be treated that way,
        you need to wrap them with `tf.convert_to_tensor`.
    *   No lowering on gradient case op when input is `DeviceIndex` op.
    *   Extend the ragged version of `tf.gather` to support `batch_dims` and
        `axis` args.
    *   Update `tf.map_fn` to support RaggedTensors and SparseTensors.