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.

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)