code: def test_gradcheck(self, device):
      img = torch.rand(1, 1, 3, 3, 3, device=device)
  
      op = kornia.metrics.ssim3d
      img = tensor_to_gradcheck_var(img)
  
      assert self.gradcheck(op, (img, img, 3), nondet_tol=1e-8)
  
imports: import pytest
  import torch
  import kornia
  from kornia.testing import BaseTester, assert_close, tensor_to_gradcheck_var
label_desc: Use image node_id 6 for calling the TestSSIM3d obj's underlying member method code with example usage: obj.test_gradcheck(device) without return types