python stub property "Unresolved Attribute Reference" in Class Implementation

I made a Class Interface in my pyi module (scheme.pyi):

class Catalog:

    @property
    def elements(self) -> List[Element]: ...

and in my scheme.py I implemented the class like this:

class Catalog:

    def __init__(self, element_collection):
        self.__elements = element_collection

    @property
    def elements(self):
        return self.__elements

PyCharm says "Unresolved Attribute Reference "__elements" for class Catalog"

I think it will work if you make Class Interface like so:

class Catalog:

    def __init__(self, element_collection) -> None:
        self.__elements: List[Element]

    @property
    def elements(self) -> List[Element]:

or you can optionally declare instance variables in the class body like so:

class Catalog:

    self.__elements: List[Element]

    @property
    def elements(self) -> List[Element]: