Function query_co_members 

pub fn query_co_members<V>(
    _q: &GraphQuery<V>,
    element: &Pattern<V>,
    container: &Pattern<V>,
) -> Vec<Pattern<V>>
where
    V: GraphValue + Clone,
    V::Id: Clone + Eq + Hash,

Returns all elements that share container with element, excluding element itself.

Co-membership is checked by identity (V::Id). The container’s elements field is traversed directly — O(k) where k = number of elements in the container.