def METHOD_NAME(dataset: Dataset) -> str:
    """Convenience function to get dataset's benchmark
    The Pbench Server intake constructs a server.benchmark metadata key to
    represent the benchmark type. This helper implements a fallback for
    datasets processed prior to the implementation of server.benchmark to
    avoid null values, by using the Pbench Agent metadata.log "script"
    value if that exists and then a constant fallback value.
    TODO: This is a workaround from the transition to server.benchmark in
    order to cleanly support earlier datasets on the staging server. This
    can be removed at some point, but it's not critical.
    Args:
        dataset: Dataset object
    Returns:
        A lowercase benchmark identifer string, including the value defined
        by Metadata.SERVER_BENCHMARK_UNKNOWN if we can't find a value.
    """
    benchmark = Metadata.getvalue(dataset, Metadata.SERVER_BENCHMARK)
    if not benchmark:
        benchmark = Metadata.getvalue(dataset, "dataset.metalog.pbench.script")
        if not benchmark:
            benchmark = Metadata.SERVER_BENCHMARK_UNKNOWN
    return benchmark