code: def test_sync_batchnorm():
      def get_num_devices():
          for i in range(100):
              try:
                  mx.np.zeros((1,), device=mx.gpu(i))
              except:
                  return i
  
      # no need to use SyncBN with 1 gpu
      if get_num_devices() < 2:
          return
      ndev = 2
      # check with unsync version
      for _ in range(10):
          _check_batchnorm_result(
              mx.np.random.uniform(size=(4, 1, 4, 4)),
              num_devices=ndev,
              cuda=True,
          )
  
imports: import sys
  import os
  import time
  import random
  import mxnet
  import multiprocessing
  from mxnet.test_utils import check_consistency, set_default_device, assert_almost_equal, rand_ndarray, environment
  import numpy
  import math
  from mxnet import autograd
  import pytest
  from common import assert_raises_cudnn_not_satisfied, run_in_spawned_process, random_seed
  from test_gluon import *
  from test_loss import *
  from test_numpy_loss import *
  from test_gluon_rnn import *
label_desc: Use image node_id 15 for calling a global function with example usage: test_sync_batchnorm() and returns: i