collect statistics from `tf.data.Dataset` pipeline using
        `StatsAggregator`. Add nested option, `experimental_stats` (which takes
        a `tf.data.experimen tal.StatsOptions` object), to `tf.data.Options`.
        Deprecates `tf.data.experimental.set_stats_agregator`.
    *   Performance optimizations:
    *   Add `tf.data.experimental.OptimizationOptions()`, to configure options