Python中的聚合OOP概念是否限制子对象不被其他对象拥有？

我读到这样的说法：“当对象具有自己的生命周期并且子对象只能与一个父对象关联时，就会发生聚合”。但是，它对我的​​代码来说很好用：-

class Country:
    def __init__(self,name=None,population=0):
        self.name = name
        self.population = population

    def printDetails(self):
        print("Country Name:",self.name)
        print("Country Population",self.population)


class Person:
    def __init__(self,name,country):
        self.name = name
        self.country = country

    def printDetails(self):
        print("Person Name:",self.name)
        self.country.printDetails()

class Man:
    def __init__(self,self.name)
        self.country.printDetails()



c = Country("Wales",1500)
p = Person("Joe",c)
m = Man('John',c);
p.printDetails()
m.printDetails()

c.printDetails()