def working(self):
        e = sqldb_ems.Element()
        e.id = 1

        session.merge(e)
        session.commit()

    def not_working(self):
        e = sqldb_ems.Element()
        e.id = 1

        ep = sqldb_ems.ElementProperty()
        ep.name = 'test'
        e.properties.append(ep)

        session.merge(e)
        session.commit()