select_alignment_pairs alignment sites doublets = builtin_select_alignment_pairs alignment sites' doublets
    where sites' = list_to_vector $ map (\(x,y) -> c_pair x y) sites
select_alignment_pairs alignment sites doublets = builtin_select_alignment_pairs alignment sites' doublets
    where sites' = list_to_vector $ map (\(x,y) -> c_pair x y) sites
select_alignment_pairs alignment sites doublets = builtin_select_alignment_pairs alignment sites' doublets
    where sites' = list_to_vector $ map (\(x,y) -> c_pair x y) sites