code: def dummy_transform(data, label):
      im = data.astype(args.dtype, copy=False) / 255 - 0.5
      im = nd.transpose(im, (2, 0, 1))
      return im, label
  
file_path: byteps/example/mxnet/train_gluon_mnist_byteps_gc.py
imports: import argparse
  import logging
  import subprocess
  import time
  import mxnet
  from mxnet import autograd, gluon, nd
  from mxnet.gluon.data.vision import MNIST
  import byteps.mxnet
label_desc: Use image node_id 1 for calling a global function with example usage: dummy_transform(data, label) and returns: im,  label