code: def test_set_default_backend():
      default_dir = os.path.join(
          os.path.expanduser("~"), ".dgl_unit_test"
      )
      F.set_default_backend(default_dir, "pytorch")
  
      # make sure the config file was created
      assert os.path.exists(os.path.join(default_dir, "config.json"))
  
label_desc: Use image node_id 1 for calling a global function with example usage: test_set_default_backend() without return types