PEP 591 specifies a final decorator that intends to restrict subsclassing for those classes with the giving decorator as well...

PEP 591 specifies a final decorator that intends to restrict subsclassing for those classes with the giving decorator as well as overriding methods with this annotation. It plays nicely with the @overload decorator, although a type checker such as mypy would require the @final decorator to be put last. As any typing implementation, it's not going to be enforced at runtime if no runtime type checker is being used. For more info, see