docs: public int compareTo(InternalFeature o) {
  		if (null == o) {
  			return -1; // avoid NPE, put null objects at the end
  		}
  		if (null != styleDefinition && null != o.getStyleInfo()) {
  			if (styleDefinition.getIndex() > o.getStyleInfo().getIndex()) {
  				return 1;
  			}
  			if (styleDefinition.getIndex() < o.getStyleInfo().getIndex()) {
  				return -1;
  			}
  		}
  		return 0;
  	}