private DecisionTree buildModel(Iterable<I> trainingData, int treeIndex) {
   logger.debug("Building oldTree {} of {}", treeIndex, numTrees);
   return treeBuilder.copy().buildPredictiveModel(trainingData);
 }
 @Override
 public void updateBuilderConfig(Map<String, Serializable> config) {
   treeBuilder.updateBuilderConfig(config);
   if (config.containsKey(NUM_TREES.name())) this.numTrees((Integer) config.get(NUM_TREES.name()));
 }