code: def tearDown(self):
      # Delete so that all the subprocesses are joined
      del self.vec_env
  
file_path: chainerrl/tests/envs_tests/test_vector_envs.py
imports: import unittest
  from chainer import testing
  import gym
  import numpy
  import chainerrl
label_desc: Use image node_id 2 for calling the TestSerialVectorEnv obj's underlying member method code with example usage: obj.tearDown() without return types