code: protected static Double sumAsDouble(final List<?> slaveValues) {
          double sum = 0;
          for (final Object slaveValue : slaveValues) {
              final Number value = (Number) slaveValue;
              if (value != null) {
                  sum += value.doubleValue();
              }
          }
          return sum;
      }
docs: Helper method to get a sum of values (sum will be calculated as a double)
  
  @param slaveValues
  @return