docs: public List<Cluster<M>> getAllClusters() {
      ArrayList<Cluster<M>> res = new ArrayList<>(hierarchy.size());
      for(It<Cluster<M>> iter = hierarchy.iterAll(); iter.valid(); iter.advance()) {
        res.add(iter.get());
      }
      Collections.sort(res, Cluster.BY_NAME_SORTER);
      return res;
    }