docs: public static void prune(TreeNodeVisitor root, PruningMethod method, ClassificationDataSet testSet)
      {
          //TODO add vargs for extra arguments that may be used by pruning methods
          if(method == PruningMethod.NONE )
              return;
          else if(method == PruningMethod.REDUCED_ERROR)
              pruneReduceError(null, -1, root, testSet);
          else if(method == PruningMethod.ERROR_BASED)
              pruneErrorBased(null, -1, root, testSet, 0.25);
          else
              throw new RuntimeException("BUG: please report");
      }