code: def transform_inverse(im_tensor, mean, std):
      
      assert im_tensor.shape[0] == 3
      im = im_tensor.transpose((1, 2, 0))
      im = im * std + mean
      im = im.astype(np.uint8)
      return im
docs: transform from mxnet im_tensor to ordinary RGB image
      im_tensor is limited to one image
      :param im_tensor: [batch, channel, height, width]
      :param mean: [RGB pixel mean]
      :param std: [RGB pixel std var]
      :return: im [height, width, channel(RGB)]