class DescriptorToNull:
    """Это класс дескриптора."""
    def __init__(self):
        self.val = None
        self.list_owner = []
    def __get__(self, instance, owner):
        return self.val
    def __set__(self, instance, value):
        instance.__dict__["n_value"] = value
        self.list_owner.append(self)  #хотела создать список владельцев,
    def null(self):
        pass  #вот здесь не понимаю что дальше
    
    def __set_name__(self, klass, name):
        self._name = name
class MyClass:
    """Это класс владелец дескрипторов."""
    core = DescriptorToNull()
    def __init__(self):
        self.n_value = None

 score = DescriptorToNull()

 t1 = MyClass()
t2 = MyClass()
t1.score = 5
print(t1.score)   #5
t2.score = 28
print(t1.score, t2.score)   # 5 28
DescriptorToNull.null()    
print(t1.score, t2.score)    # 0 0
del team2.score

 class DescriptorToNull:
    list_owner = {}
    def __get__(self, instance, owner):
        return instance.n_value
  
    def __set__(self, instance, value):
        instance.n_value = value
        self.list_owner[id(instance)] = instance
        
    def __delete__(self, instance):
        del self.list_owner[id(instance)]
    
    @classmethod
    def null(cls):
        for x in cls.list_owner:
            cls.list_owner[x].n_value = 0
 
class MyClass:
    score = DescriptorToNull()
    def __init__(self):
        self.n_value = 0

 class DescriptorToNull:
    dict_instances = {}
    name = None
    def __get__(self, instance, owner):
        return instance.name
    def __set__(self, instance, value):
        instance.name = value
        self.dict_instances[id(instance)] = instance
    def __delete__(self, instance):
        del self.dict_instances[id(instance)]
    def __set_name__(self, owner, name):
        self.name = name
    @classmethod
    def null(cls):
        for x in cls.dict_instances:
            cls.dict_instances[x].name = 0
class MyClass:
    score = DescriptorToNull()
    def __init__(self):
        self.score = 0