code: def test_forward_nu_1_over_2(self):
      a = torch.tensor([4, 2, 8], dtype=torch.float).view(3, 1)
      b = torch.tensor([0, 2], dtype=torch.float).view(2, 1)
      lengthscale = 2
  
      kernel = MaternKernel(nu=0.5).initialize(lengthscale=lengthscale)
      kernel.eval()
  
      actual = (
          torch.tensor([[4, 2], [2, 0], [8, 6]], dtype=torch.float)
          .div_(-lengthscale)
          .exp()
      )
      res = kernel(a, b).to_dense()
      self.assertLess(torch.norm(res - actual), 1e-3)
  
imports: import math
  import pickle
  import unittest
  import torch
  from gpytorch.kernels import MaternKernel
  from gpytorch.priors import NormalPrior
  from gpytorch.test.base_kernel_test_case import BaseKernelTestCase
label_desc: Use image node_id 3 for calling the TestMaternKernel obj's underlying member method code with example usage: obj.test_forward_nu_1_over_2() without return types