Parameters
        ----------
        sid : int
            The asset identifier.
        day : datetime64-like
            Midnight of the day for which data is requested.
        field : string
            The price field. e.g. ('open', 'high', 'low', 'close', 'volume')

        Returns
        -------
        float
            The spot price for colname of the given sid on the given day.
            Raises a NoDataOnDate exception if the given day and sid is before
            or after the date range of the equity.
            Returns -1 if the day is within the date range, but the price is
            0.

def get_value(self, sid, dt, field):
        """
        Parameters
        ----------
        sid : int
            The asset identifier.
        day : datetime64-like
            Midnight of the day for which data is requested.
        field : string
            The price field. e.g. ('open', 'high', 'low', 'close', 'volume')

        Returns
        -------
        float
            The spot price for colname of the given sid on the given day.
            Raises a NoDataOnDate exception if the given day and sid is before
            or after the date range of the equity.
            Returns -1 if the day is within the date range, but the price is
            0.
        """
        return self.frames[field].loc[dt, sid]