def exist(self, item_name, index=None):
        if item_name in self.db:
            if index is not None:
                try:
                    self.db[item_name]['value'][index]
                except __HOLE__:
                    return False
            return True
        return False
dataset/ETHPy150Open nyddle/pystash/pystash/common.py/ShelveStorage.exist