code: def get_value(self, continuous_future, dt, field):
          
          rf = self._roll_finders[continuous_future.roll_style]
          sid = (rf.get_contract_center(continuous_future.root_symbol,
                                        dt,
                                        continuous_future.offset))
          return self._bar_reader.get_value(sid, dt, field)
docs: Retrieve the value at the given coordinates.
  
          Parameters
          ----------
          sid : int
              The asset identifier.
          dt : pd.Timestamp
              The timestamp for the desired data point.
          field : string
              The OHLVC name for the desired data point.
  
          Returns
          -------
          value : float|int
              The value at the given coordinates, ``float`` for OHLC, ``int``
              for 'volume'.
  
          Raises
          ------
          NoDataOnDate
              If the given dt is not a valid market minute (in minute mode) or
              session (in daily mode) according to this reader's tradingcalendar.