Protocol and final instance attributes

Is there a way to mark in a Protocol that an attribute is a final instance attribute? Basically I would like for

class A:
    def __init__(self, b; int):
        self.b: Final[int] = b

To be a structural subtype of something like

class Y(Protocol):
    b: Final[int]  # Or something else

but in that case, b is interpreted as a class attribute by type checkers.

I have also tried

class Y(Protocol):
    def b(self) -> int:
        raise NotImplementedError

But at least Pylance does not allow consider A as a structural subtype of Y then.