code: def train_op(x, y, lr):
      g, v = gv(x, y)
      opt(lr=lr, grads=g)
      return v
  
file_path: objax/examples/image_classification/cifar10_simple.py
imports: import random
  import numpy
  import tensorflow
  import objax
  from objax.zoo.wide_resnet import WideResNet
label_desc: Use image node_id 2 for calling a global function with example usage: train_op(x, y, lr) and returns: v