code: public String[] makeSvmLabelMap() {
      String[] labelMap = new String[numClasses()];
      if (numClasses() > 2) {
        for (int i = 0; i < labelMap.length; i++) {
          labelMap[i] = String.valueOf((i + 1));
        }
      } else {
        labelMap = new String[]{"+1", "-1"};
      }
      return labelMap;
    }
docs: Maps our labels to labels that are compatible with svm_light
  @return array of strings