node.removeMixin("mix:sharable");
session.save();

gives me:
Unable to save: javax.jcr.UnsupportedRepositoryOperationException:
Removing mix:shareable is not supported.

Is there a way around it?
I don't want to delete the node and recreate it. it has so many
children. I just wanted to try mix:sharable ... But I don't want it
anymore.