code: def _haveKey(self, key):
          
          query = (
              "SELECT {} FROM {} WHERE {}=?".format(
                  self.__value__, self.__tablename__, self.__key__
              ),
              (key,),
          )
          connection = sqlite3.connect(self.sqlite_file)
          cursor = connection.cursor()
          cursor.execute(*query)
          return True if cursor.fetchone() else False
docs: Is the key `key` available?