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