code: def test_forward_vec(self):
      pass
  
imports: import unittest
  import torch
  from gpytorch.means import ConstantMean, MultitaskMean, ZeroMean
  from gpytorch.test.base_mean_test_case import BaseMeanTestCase
label_desc: Use image node_id 2 for calling the TestMultitaskMeanBatch obj's underlying member method code with example usage: obj.test_forward_vec() without return types