Parameters:
      device (device or string) -- the device to set as
      default
Example:
  >>> torch.tensor([1.2, 3]).device
  device(type='cpu')
  >>> torch.set_default_device('cuda')  # current device is 0
  >>> torch.tensor([1.2, 3]).device
  device(type='cuda', index=0)
  >>> torch.set_default_device('cuda:1')
  >>> torch.tensor([1.2, 3]).device
  device(type='cuda', index=1)
