Function pair_probs2avg_probs 

pub fn pair_probs2avg_probs<T>(
    alignfold_probs_hashed_ids: &HashMap<(usize, usize), AlignfoldProbMats<T>>,
    rna_id: usize,
    num_rnas: usize,
    unpair_probs_len: usize,
    produces_context_profs: bool,
) -> AlignfoldProbMatsAvg<T>
where
    T: HashIndex,