code: def test_ext_user_sigmoid(device_id):
      exp_losses, exp_errors = train(sigmoid, 4, device_id)
      act_losses, act_errors = train(MySigmoid, 4, device_id)
      assert np.allclose(exp_losses, act_losses)
      assert np.allclose(exp_errors, act_errors)
  
imports: from __future__ import division, print_function
  import numpy
  import cntk
  from cntk.ops.tests.ops_test_utils import cntk_device, mem_used, os_process
  from cntk.ops.functions import UserFunction
  from cntk import sigmoid
label_desc: Use image node_id 8 for calling a global function with example usage: test_ext_user_sigmoid(device_id) without return types