docs: private ClassicCounter<Pair<F, L>> convertSVMLightWeights(ClassicCounter<Integer> weights, Index<F> featureIndex, Index<L> labelIndex) {
      ClassicCounter<Pair<F, L>> newWeights = new ClassicCounter<Pair<F, L>>();
      for (int i : weights.keySet()) {
        F f = featureIndex.get(i-1);
        double w = weights.getCount(i);
        // the first guy in the labelIndex was the +1 class and the second guy
        // was the -1 class
        newWeights.incrementCount(new Pair<F, L>(f, labelIndex.get(0)),w);
        newWeights.incrementCount(new Pair<F, L>(f, labelIndex.get(1)),-w);
      }
      return newWeights;
    }