code: def test_forward_mat_multi_batch(self):
      test_x = torch.randn(2, 3, 4, 3)
      mean = self.create_mean()
      self.assertEqual(mean(test_x).shape, torch.Size([2, 3, 4, 4]))
      self.assertEqual(mean(test_x)[..., 1:].norm().item(), 0)
  
file_path: gpytorch/test/means/test_constant_mean_grad.py
imports: import unittest
  import torch
  from gpytorch.means import ConstantMeanGrad
  from gpytorch.test.base_mean_test_case import BaseMeanTestCase
label_desc: Use image node_id 5 for calling the TestConstantMeanGrad obj's underlying member method code with example usage: obj.test_forward_mat_multi_batch() without return types