Function for_hashset_get 

pub fn for_hashset_get<T>(
    value: T,
) -> OptionalKeyPath<HashSet<T>, T, impl for<'r> Fn(&'r HashSet<T>) -> Option<&'r T>>
where
    T: Hash + Eq + Clone + 'static,

Create a keypath for getting a value from HashSet (returns Option<&T>)