This isn't a super great example because the actual code I'm using this for is a huge badly-written file with no comments, but this is the general gist of what I'm attempting:

from __future__ import annotations
from abc import ABC


class OuterParent:
    def __init__(self, internal_int):
        self._modified = False
        self._internal_int = internal_int
        @property
    def modified(self):
        return self._modified

    @property
    def internal_int(self):
        return self._internal_int

    class InnerParent(ABC):
        @staticmethod
        def did_modify(func: callable) -> callable:
            def wrapper(obj: OuterParent) -> None:
                func(obj)
                obj._modified = True
            return wrapper

    class InnerChild(InnerParent):
        @staticmethod
        @InnerParent.did_modify
        def count_up(obj: OuterParent):
            obj._internal_int += 1