code: def test_all_devices():
      assert len(C.device.all_devices()) > 0
      assert C.cpu() in C.device.all_devices()
      if len(C.device.all_devices()) > 1:
          assert C.gpu(0) in C.device.all_devices()
  
imports: import numpy
  import pytest
  import cntk
  from multiprocessing import Process, Queue
label_desc: Use image node_id 6 for calling a global function with example usage: test_all_devices() without return types