@Override
 public void write(final NumberStatistics s, final OutputElement xml)
     throws XMLStreamException {
   Statistics.XML.write(s, xml);
   xml.add(Float64.valueOf(s.getFitnessMean()), FITNESS_MEAN);
   xml.add(Float64.valueOf(s.getFitnessVariance()), FITNESS_VARIANCE);
   xml.add(Float64.valueOf(s.getStandardError()), ERROR_OF_MEAN);
 }
        @Override
        public NumberStatistics newInstance(
            final Class<NumberStatistics> type, final InputElement xml) throws XMLStreamException {
          final Statistics stats = Statistics.XML.newInstance(Statistics.class, xml);
          final Float64 fitnessMean = xml.get(FITNESS_MEAN);
          final Float64 fitnessVariance = xml.get(FITNESS_VARIANCE);
          final Float64 errorOfMean = xml.get(ERROR_OF_MEAN);

          final Builder builder = new Builder().statistics(stats);
          builder.fitnessMean(fitnessMean.doubleValue());
          builder.fitnessVariance(fitnessVariance.doubleValue());
          builder.standardError(errorOfMean.doubleValue());

          return builder.build();
        }