class Scene:
    def __init__(self):
        self.entities = {}

    def add(self, entity):
        self.entities[entity.name] = entity
        entity.scene = self
        entity.load()

    def unload(self):
        for entity in self.entities.values():
            entity.unregister()

    def load(self):
        for entity in self.entities.values():
            entity.register()