docs: public static List<Clustering<? extends Model>> getClusteringResults(Result r) {
      if(r instanceof Clustering<?>) {
        List<Clustering<?>> crs = new ArrayList<>(1);
        crs.add((Clustering<?>) r);
        return crs;
      }
      if(r instanceof HierarchicalResult) {
        return ResultUtil.filterResults(((HierarchicalResult) r).getHierarchy(), r, Clustering.class);
      }
      return Collections.emptyList();
    }