docs: public Object getAt(int index) {
          try {
              // a negative index will count backwards from the last column.
              if (index < 0)
                  index += result.size();
              Iterator it = result.values().iterator();
              int i = 0;
              Object obj = null;
              while ((obj == null) && (it.hasNext())) {
                  if (i == index)
                      obj = it.next();
                  else
                      it.next();
                  i++;
              }
              return obj;
          }
          catch (Exception e) {
              throw new MissingPropertyException(Integer.toString(index), GroovyRowResult.class, e);
          }
      }