Return the next result value in the sequence. Raise
        StopIteration at the end. Can raise the exception raised by
        the Job

def next(self, timeout=None):
        """Return the next result value in the sequence. Raise
        StopIteration at the end. Can raise the exception raised by
        the Job"""
        try:
            apply_result = self._collector._get_result(self._idx, timeout)
        except IndexError:
            # Reset for next time
            self._idx = 0
            raise StopIteration
        except:
            self._idx = 0
            raise
        self._idx += 1
        assert apply_result.ready()
        return apply_result.get(0)