Function merge_alignfolds 

pub fn merge_alignfolds<T, U>(
    alignfold_pair: &AlignfoldPair<'_, T, U>,
    match_probs_hashed_ids: &SparseProbsHashedIds<T>,
    basepair_prob_mats: &SparseProbMats<T>,
    alignfold_hyperparams: &AlignfoldHyperparams,
    insert_probs_pairs_hashed: &ProbsPairsHashedIds,
    ends_alignfold: bool,
) -> AlignfoldWrapped<T, U>
where
    T: HashIndex,
    U: HashIndex,