code: def test_set_gpu_as_default_device():
      if len(C.device.all_devices()) == 1:
          return
      # this will release any previous held device locks
      C.try_set_default_device(C.cpu(), False)
      for i in range(len(C.device.all_devices()) - 1):
          device = C.gpu(i)
          assert C.try_set_default_device(device, False)
          assert not is_locked(device)
          assert device == C.use_default_device()
          if not device.is_locked():
              assert not is_locked(device)
              assert C.try_set_default_device(device, True)
              assert device == C.use_default_device()
              assert is_locked(device)
  
imports: import numpy
  import pytest
  import cntk
  from multiprocessing import Process, Queue
label_desc: Use image node_id 11 for calling a global function with example usage: test_set_gpu_as_default_device() without return types