Function saboten::cactusgraph::chain_pair_contained_ultrabubbles

pub fn chain_pair_contained_ultrabubbles(
    cactus_tree: &CactusTree<'_>, 
    chain_pairs: &FnvHashSet<ChainPair>, 
    chain_edge_labels: &mut FnvHashMap<(u64, u64), bool>
) -> FnvHashMap<(u64, u64), Vec<(u64, u64)>>

Using the provided chain edge labels, returns a map from chain pairs to contained ultrabubbles. Each entry is an ultrabubble, if the entry has an empty vector, it doesn't contain any ultrabubbles.