code: def normalize(train_x, val_x):
      train_x /= 255
      val_x /= 255
      return train_x, val_x
  
file_path: singa/examples/cifar_distributed_cnn/data/mnist.py
imports: import numpy
  import os
  import sys
  import gzip
  import codecs
label_desc: Use image node_id 6 for calling a global function with example usage: normalize(train_x, val_x) and returns: train_x,  val_x