(very internal) returns the next result, given ``"stride"`` and ``"n"``.

def next(self):
        """
        (very internal) returns the next result, given ``"stride"`` and ``"n"``.
        
        """
        try:
            res, excp = self._stride_buffer.next()
        except (StopIteration, AttributeError):
            try:
                self._stride_buffer = izip(*self._repeat_buffer.next())
            except (StopIteration, AttributeError):
                self._rebuffer()
                self._stride_buffer = izip(*self._repeat_buffer.next())
            res, excp = self._stride_buffer.next()
        if excp:
            raise res
        else:
            return res