code: def test_set_cpu_as_default_device():
      device = C.cpu()
      assert not is_locked(device)
      assert not C.try_set_default_device(device, True)
      assert not is_locked(device)
      assert C.try_set_default_device(device)
      assert C.try_set_default_device(device, False)
      assert not is_locked(device)
      assert device == C.use_default_device()
  
imports: import numpy
  import pytest
  import cntk
  from multiprocessing import Process, Queue
label_desc: Use image node_id 10 for calling a global function with example usage: test_set_cpu_as_default_device() without return types