How to use return type changed in decorator?

[MisLink]

I have a function like this:

@change_return_annotation(str)
def my_function(x: int, y: int) -> int:
    return x + y

The decorator change the return annotation:

def change_return_annotation(new_return_annotation):
    def decorator(func):
        func.__annotations__['return'] = new_return_annotation
        @functools.wrap(func)
        def wrapper(*args, **kwargs):
            return str(func((args, **kwargs))
        return func
    return decorator

I'd like to show the changed return type in mkdocs. It seems that I need to use InspectorExtension to let griffe import the code. Then I try to create one:

class Inspect(InspectorExtension):
    def inspect_function(self, node: ObjectNode) -> None:
        function: Function = self.inspector.current.members[node.name]  # type: ignore
        for decorator in function.decorators:
            ret = node.obj.__annotations__["return"]
            # not work
            # function.returns = ret


class HybridExtension(hybrid.HybridExtension):
    def __init__(self) -> None:
        super().__init__([Inspect()])


Extension = HybridExtension

Here I'm stuck. How to get an AST node for ret, or do I totally do the wrong thing?