presto-main/src/main/java/io/prestosql/operator/TransformWork.java/TransformWork/TransformWork
class TransformWork:    public TransformWork(Work<I> work, Function<I, O> transformation)
    {
        this.work = requireNonNull(work, "work is null");
        this.transformation = requireNonNull(transformation, "transformation is null");
    }