Tensor already matches the desired conversion.
Example:
  >>> tensor = torch.randn(2, 2)  # Initially dtype=float32, device=cpu
  >>> tensor.to(torch.float64)
  tensor([[-0.5044,  0.0005],
          [ 0.3310, -0.0584]], dtype=torch.float64)

  >>> cuda0 = torch.device('cuda:0')
  >>> tensor.to(cuda0)
  tensor([[-0.5044,  0.0005],
          [ 0.3310, -0.0584]], device='cuda:0')

  >>> tensor.to(cuda0, dtype=torch.float64)
  tensor([[-0.5044,  0.0005],
          [ 0.3310, -0.0584]], dtype=torch.float64, device='cuda:0')

  >>> other = torch.randn((), dtype=torch.float64, device=cuda0)
  >>> tensor.to(other, non_blocking=True)
  tensor([[-0.5044,  0.0005],
          [ 0.3310, -0.0584]], dtype=torch.float64, device='cuda:0')
