pub fn remove_eq_rec<Q, K, V>(
    node: &Node<K, V>,
    h: HashedKey,
    lvl: usize,
    k: &Q,
    v: &V
) -> Result<Option<Node<K, V>>, RemoveError>where
    Q: PartialEq,
    K: Borrow<Q> + PartialEq + Clone,
    V: PartialEq + Clone,