@Uncommonly used nickname. Let me tell you, welcome to discuss

If I understand correctly, the original English name of Decoration class in the original post "2. Decoration class: the object to be decorated is a class" should be Class Decorators.
According to the syntax requirements, the format of class decorators is as follows:

#定义
def decorator(C):
#process class C
    return C

#使用
@decorator
class C:...    

Reference material "Learning Python 5E" page1277-1278

So, the definition of class decorator in the question is completely wrong.
It should be in the following form:

def test(cls):
    class C():
#   class C 的定义填在这里。 
    return C

sy is a class. Implement the __call__ method.

 class Sy(object):
    value=32

    def __call__(self, _class):
        pass