docs: public DataSet getTwiceShallowClone()
      {
          DataSet clone = shallowClone();
          for(int i = 0; i < clone.size(); i++)
          {
              DataPoint d = getDataPoint(i);
              DataPoint sd = new DataPoint(d.getNumericalValues(), d.getCategoricalValues(), d.getCategoricalData());
              clone.setDataPoint(i, sd);
          }
          return clone;
      }