宠物商店：实现一个宠物商店，制定了宠物标准接口后，程序可添加任何具体的宠物对象，并且可搜索已添加在宠物商店中的宠物。(Pet store: after implementing a pet store and setting up a pet standard interface, the program can add any specific pet object and search for pets that have been added to pet shops.)