code: def test_gradcheck(self, device):
      def proxy_func(pts, weights):
          line = fit_line(pts, weights)
          return line.projection(pts[:, 0].T)
  
      pts = torch.rand(
          1,
          3,
          2,
          device=device,
          dtype=torch.float64,
          requires_grad=True,
      )
      weights = torch.rand(
          1, 3, device=device, dtype=torch.float64, requires_grad=False
      )
      assert gradcheck(proxy_func, (pts, weights), raise_exception=True)
  
imports: import pytest
  import torch
  from torch.autograd import gradcheck
  from kornia.geometry.line import ParametrizedLine, fit_line
  from kornia.geometry.plane import Hyperplane
  from kornia.testing import BaseTester, assert_close
label_desc: Use image node_id 4 for calling the TestFitLine obj's underlying member method code with example usage: obj.test_gradcheck(device) and returns: line