docs: def register_new(self, entity_class, entity):
          """
          Registers the given entity for the given class as NEW.
  
          :raises ValueError: If the given entity already holds state that was
            created by another Unit Of Work.
          """
          EntityState.manage(entity, self)
          EntityState.get_state(entity).status = ENTITY_STATUS.NEW
          self.__entity_set_map[entity_class].add(entity)