docs: def col(self, col_name_or_num):
          """
          Returns the col at index `colnum` or name `colnum`.
          """
          if isinstance(col_name_or_num, basestring):
              return self[col_name_or_num]
          elif isinstance(col_name_or_num, (int, long)):
              if col_name_or_num > len(self.fields):
                  raise IndexError("Invalid column index `%s` for DataTable" %
                                   col_name_or_num)
              return self.__data[self.fields[col_name_or_num]]