code: def KeyValue(self, row=None):
          
          if not row:
              if self._iterator:
                  # If we are inside an iterator use current row iteration.
                  row = self[self._iterator]
              else:
                  row = self.row
          # If no superkey then use row number.
          if not self.superkey:
              return ["%s" % row.row]
  
          sorted_list = []
          for header in self.header:
              if header in self.superkey:
                  sorted_list.append(row[header])
          return sorted_list
docs: Returns the super key value for the row.