code: def calc_norm_diff(data1, data2):
      std1 = np.std(data1.flatten())
      std2 = np.std(data2.flatten())
      std = max(std1, std2)
      diff_std = np.std(data1.flatten() - data2.flatten())
      norm_diff = (diff_std / std) if std > 0 else 0
      return norm_diff, std1, std2, diff_std
  
file_path: nnabla/python/src/nnabla/utils/cli/compare_with_cpu.py
imports: import os
  from collections import OrderedDict
  import nnabla
  import nnabla.utils.load
  import numpy
  from contextlib2 import ExitStack
  from nnabla.logger import logger
  from nnabla.parameter import get_parameters
  from nnabla.utils.cli.utility import let_data_to_variable
  from nnabla.utils.progress import configure_progress, progress
label_desc: Use image node_id 2 for calling a global function with example usage: calc_norm_diff(data1, data2) and returns: norm_diff,  std1,  std2,  diff_std