children.add(child2);
parent.setChildren(children);
PersistenceManager pm = pmf.getPersistenceManager();
FetchPlan fp = pm.getFetchPlan();
fp.removeGroup("default").addGroup("none");
pm.currentTransaction().begin();
logger.log(BasicLevel.DEBUG, "make persistent the person " + parent.toString());
pm.makePersistent(parent);
pm.currentTransaction().commit();