private static double getCohesionIndex(@NotNull UsageCluster cluster, @NotNull SimilarUsage similarUsage) {
    Ref<Double> cohesionIndex = new Ref<>(0.0);
    cluster.getUsages()
      .forEach(usage -> {
        cohesionIndex.set(cohesionIndex.get() + jaccardDistanceExact(usage.getFeatures(), similarUsage.getFeatures()));
      });

    return cohesionIndex.get() / (cluster.getUsages().size() - 1);
  }
private static double getCohesionIndex(@NotNull UsageCluster cluster, @NotNull SimilarUsage similarUsage)