code: def test_grid_grid(self, toeplitz=True):
      with gpytorch.settings.use_toeplitz(toeplitz):
          base_kernel = RBFKernel(ard_num_dims=2)
          kernel = GridKernel(base_kernel, grid)
          grid_covar = kernel(grid_data, grid_data).evaluate_kernel()
          self.assertIsInstance(
              grid_covar, KroneckerProductLinearOperator
          )
          grid_eval = kernel(grid_data, grid_data).to_dense()
          actual_eval = base_kernel(grid_data, grid_data).to_dense()
          self.assertLess(torch.norm(grid_eval - actual_eval), 2e-5)
  
file_path: gpytorch/test/kernels/test_grid_kernel.py
imports: import unittest
  import torch
  from linear_operator.operators import KroneckerProductLinearOperator
  import gpytorch
  from gpytorch.kernels import GridKernel, LinearKernel, RBFKernel
  from gpytorch.utils.grid import create_data_from_grid
label_desc: Use image node_id 1 for calling the TestGridKernel obj's underlying member method code with example usage: obj.test_grid_grid(toeplitz) without return types