code: @Override
      public Double reduce(List<Double> values) {
          double min = Double.MAX_VALUE;
          double max = Double.MIN_VALUE;
  
          for (Double value : values) {
              if (value == null) {
                  value = 0.0;
              }
  
              double candidate = (value);
  
              if (candidate < min) {
                  min = candidate;
              }
              if (candidate > max) {
                  max = candidate;
              }
          }
          return max - min;
      }
docs: ~ Methods **************************************************************************************************************************************