Proxy class to track modifications in a Python object and its children

proxy.py

class Proxy:
    """
    Wraps an object to keep track of modifications, including to its children.
    """
    def __init__(self, obj, modified_flag=None):
        # Must use `super().__setattr__` to avoid recursing on itself.
        super().__setattr__('_obj', obj)
        super().__setattr__('_modified_flag', modified_flag or [False])

    @property
    def is_modified(self):
        """ Returns True if any object in this tree has been modified. """
        return self._modified_flag[0]

    def _set_modified(self):
        self._modified_flag[0] = True

    def _wrap_subvalue(self, value):
        """
        Given an attribute or index value, decides if it should be returned as-is
        (e.g. primitive types), wrapped in another Proxy (e.g. substructures), or 
        if it's a modifying function call and the respective flag should be set.
        """
        if isinstance(value, (int, str, float, bool, bytes)):
            return value
        elif callable(value):
            # List of functions that modify the object.
            if value.__qualname__ in ('list.append', 'list.pop', 'list.clear', 'list.extend', 'list.insert', 'list.remove', 'list.sort', 'list.reverse', 'dict.popitem', 'dict.update', 'dict.pop', 'dict.clear'):
                self._set_modified()
            return value
        else:
            return Proxy(obj=value, modified_flag=self._modified_flag)

    def __getattr__(self, name):
        return self._wrap_subvalue(getattr(self._obj, name))

    def __setattr__(self, name, value):
        self._set_modified()
        setattr(self._obj, name, value)

    def __getitem__(self, index):
        return self._wrap_subvalue(self._obj[index])

    def __setitem__(self, index, value):
        self._set_modified()
        self._obj[index] = value


if __name__ == '__main__':
    ###
    # Example usage
    ###

    from dataclasses import dataclass

    @dataclass
    class Child:
        value: float

    @dataclass
    class Parent:
        """Class for keeping track of an item in inventory."""
        name: str
        children: [Child]

        def bogus_operation(self) -> float:
            return sum(child.value for child in self.children) / len(self.children)

    parent = Proxy(Parent('parent name', [Child(value=5), Child(value=4)]))
    parent.bogus_operation()
    print(parent.is_modified)
    parent.children[0].value = 2
    parent.children.append(Child(1))
    print(parent.is_modified)