def get_etag(self, href, calendar):
        """get etag for href

        type href: str()
        return: etag
        rtype: str()
        """
        sql_s = 'SELECT etag FROM events WHERE href = ? AND calendar = ?;'
        try:
            etag = self.sql_ex(sql_s, (href, calendar))[0][0]
            return etag
        except __HOLE__:
            return None
dataset/ETHPy150Open pimutils/khal/khal/khalendar/backend.py/SQLiteDb.get_etag