<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def tuple_len(self):
 """ Length of tuples produced by this generator. """

        try:
            return self._tuple_len
        except AttributeError:
            raise NotImplementedError("Class {} does not implement attribute 'tuple_len'.".format(self.__class__.__name__))