code: def get_field_names(self):
          
          if self.add:
              return ['date', 'elem', 'value'] + [flag for flag in self.add]
          else:
              field_names = ['date']
              for elem in self.parameter:
                  # namedtuple doesn't like numeric field names
                  if elem.isdigit():
                      elem = "e%s" % elem
                  field_names.append(elem)
              return field_names
docs: Different field names depending on self.add setting (see load_data)
          For BaseIO