code: def gradcheck(self, device):
      coeffs = torch.rand(
          1, 4, device=device, dtype=torch.float64, requires_grad=True
      )
      assert gradcheck(
          solver.solve_cubic,
          (coeffs),
          raise_exception=True,
          fast_mode=True,
      )
  
file_path: kornia/test/geometry/solvers/test_polynomial_solver.py
imports: import pytest
  import torch
  from torch.autograd import gradcheck
  import kornia.geometry.solvers
  from kornia.testing import assert_close
label_desc: Use image node_id 4 for calling the TestCubicSolver obj's underlying member method code with example usage: obj.gradcheck(device) without return types