Github user osma commented on the issue:
https://github.com/apache/jena/pull/503
Looks good to me, based on a quick look at the diff. It took a while to
figure out the way you use UnaryOperator but in the end it made sense.
I'm currently travelling and haven't found time to actually run the code,
but if it passes the existing unit tests and you're sure that they trigger the
`concreteSubject` case, I'm fine with that.---
