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.

def get_value(self, continuous_future, dt, field):
        """
        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.
        """
        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)