code: public List<ClassificationDataSet> trainC(ClassificationDataSet dataPoints, Set<Integer> options)
      {
          return trainC(dataPoints, options, false);
      }
docs: This is a helper function that does the work of training this stump. It may be
  called directly by other classes that are creating decision trees to avoid
  redundant repackaging of lists.
  
  @param dataPoints the lists of datapoint to train on, paired with the true category of each training point
  @param options the set of attributes that this classifier may choose from. The attribute it does choose will be removed from the set.
  @return the a list of lists, containing all the datapoints that would have followed each path. Useful for training a decision tree