code: public DataPointPair<Double> getDataPointPair(int i)
      {
          return new DataPointPair<>(getDataPoint(i), targets.get(i));
      }
docs: Returns the i'th data point in the data set paired with its target regressor value.
  Modifying the DataPointPair will effect the data set.
  
  @param i the index of the data point to obtain
  @return the i'th DataPOintPair