code: def append_delta_index(self, ts_data=None, data_delta=None, key=KEY_DATA):
          
          reasign = False
          if data_delta is None:
              if self.data is not None:
                  data_delta = self.data[key]
              else:
                  self.printif('NO HAY DATOS PARA AÑADIR DELTA', 'error')
                  return None
              reasign = True
          data_delta['delta'] = data_delta.index.tz_convert('UTC')
          if ts_data is not None:
              data_delta['delta'] = (data_delta['delta'] - data_delta['delta'].shift(1)).fillna(ts_data)
              data_delta['delta_T'] = data_delta['delta'].apply(lambda x: pd.Timedelta(x).seconds) / ts_data
          else:
              data_delta['delta'] = (data_delta['delta'] - data_delta['delta'].shift(1)).fillna(0)
          if reasign:
              self.data[key] = data_delta
          else:
              return data_delta
docs: Append columns with ∆T between rows to data.