Returns a DataSwim instance with rows in a date range

def daterange_(self, datecol, date_start, op, **args):
        """
        Returns a DataSwim instance with rows in a date range
        """
        df = self._daterange(datecol, date_start, op, **args)
        if df is None:
            self.err("Can not select date range data")
        return self._duplicate_(df)