@Override
    default Client<? extends Request, ? extends Response> unwrap() {
        return (Client<? extends Request, ? extends Response>) Unwrappable.super.unwrap();
    }
Unwraps this {@link Client} and returns the object being decorated.
If this {@link Client} is the innermost object, this method returns itself.
core/src/main/java/com/linecorp/armeria/client/Client.java