*/
public String saveLibrary() {
/* dont forget to prepare changed entities e.g. set current user */
PrepareChangesForPersist prep = new PrepareChangesForPersist(user.getUsername());
if (fragmentRoot != null) {
prep.prepare(fragmentRoot);
em.persist(em.merge(fragmentRoot));
}
if (templateRoot != null) {
prep.prepare(templateRoot);
em.persist(em.merge(templateRoot));