docs: public List<double[]> addToClusteringCenters(List<double[]> clustering) {
  		if (center != null && getClusteringFeature() != null) {
  			clustering.add(getClusteringFeature().toClusterCenter());
  		}
  		for (ClusteringTreeNode child : children) {
  			child.addToClusteringCenters(clustering);
  		}
  		return clustering;
  	}