code: public static Object sum(Object[] self, Object initialValue) {
          return sum(toList(self), initialValue, false);
      }
docs: Sums the items in an array, adding the result to some initial value.
  
  @param self         an array of values to sum
  @param initialValue the items in the array will be summed to this initial value
  @return The sum of all of the items.
  @since 1.7.1