public List<LoginPeriod> getLoginPeriodsWithoutInvitationPeriods() {
public Set<LoginPeriod> getLoginPeriodsWithoutInvitationPeriods() {
    public List<LoginPeriod> getLoginPeriodsWithoutInvitationPeriods() {	Person person = getUser().getPerson();	Login login = person.getLoginIdentification();	List<LoginPeriod> loginPeriods = login.getLoginPeriods();	for (Invitation invitation : person.getInvitationsOrderByDate()) {	    LoginPeriod period = login.readLoginPeriodByTimeInterval(invitation.getBeginDate(),		    invitation.getEndDate());	    if (period != null) {		loginPeriods.remove(period);	    }	}	return loginPeriods;    }