human
2.1 标准库中的装饰器

classmethod   

方法中如果标记为 @classmethod 那么该函数将被类调用，而不是被类的实例对象调用。该方法参数中不用self,而是cls"
Please write code following the instructions in jupyter notebook style.
 Give me a code to 2?
assistant
#Here is code to 2.

class A(object):
    def __init__(self,args):
        self._args = args
    @classmethod
    def say(cls):
        print 'say hello'
A.say()