'Move iterator position forward'

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
