__name__ is the class name; 返回类名
__module__ is the module name in which the class was defined; 定义此类的模块名
__dict__ is the dictionary containing the class’s namespace; 由类的命名空间组成的字典
__bases__ is a tuple (possibly empty or a singleton) containing the base classes, in the order of their occurrence in the base class list; 一个由基本类组成的数组（也许是空的或只有一个成员），按基类列表中出现的顺序排列
__doc__ is the class’s documentation string, or None if undefined. 类的文档字符串，如果没有定义的话，为空。