code: def next(self):
          
          batch = mx.nd.zeros((self.batch_size, self.size[1], self.size[0], 3))
          i = self.cur
          for i in range(self.cur, min(len(self.list), self.cur+self.batch_size)):
              str_img = open(self.root+self.list[i]+'.jpg').read()
              img = imdecode(str_img, 1)
              img, _ = random_crop(img, self.size)
              batch[i - self.cur] = img
          batch = mx.nd.transpose(batch, axes=(0, 3, 1, 2))
          ret = mx.io.DataBatch(data=[batch],
                                label=[],
                                pad=self.batch_size-(i-self.cur),
                                index=None)
          self.cur = i
          return ret
docs: Move iterator position forward