- required:
                                  - prefix
                                - required:
                                  - regex
                            - required:
                              - exact
                            - required:
                              - prefix
                            - required:
                              - regex

                                - required:
                                  - prefix
                                - required:
                                  - regex
                            - required:
                              - exact
                            - required:
                              - prefix
                            - required:
                              - regex

        `padded_batch()`. This functionality can be enabled through
        `tf.data.Options()`.
    *   Support cancellation of long-running `reduce`.
    *   Now we use `dataset` node name as prefix instead of the op name, to
        identify the component correctly in metrics, for pipelines with repeated
        components.
    *   Improve the performance of datasets using `from_tensors()`.