code: def next(self):
          
          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
docs: (very internal) returns the next result, given ``"stride"`` and ``"n"``.