code: def normalize(v):
      assert isinstance(v, tf.Tensor)
      v.get_shape().assert_has_rank(4)
      return v / tf.reduce_mean(v, axis=[1, 2, 3], keepdims=True)
  
imports: import argparse
  import numpy
  import os
  import cv2
  import six
  import tensorflow
  from tensorpack import *
  from tensorpack.tfutils.scope_utils import auto_reuse_variable_scope
  from tensorpack.tfutils.summary import add_moving_summary
  from tensorpack.utils import logger
  from tensorpack.utils.gpu import get_num_gpu
  from data_sampler import CenterSquareResize, ImageDataFromZIPFile, ImageDecode, RejectTooSmallImages
  from GAN import GANModelDesc, SeparateGANTrainer
label_desc: Use image node_id 1 for calling a global function with example usage: normalize(v) and returns: unknown