class_docstr: Mixin for testing batch training.
  
  Inherit this after _TestTraining to enable test cases for batch training.
class_docstr_tok: ["Mixin","for","testing","batch","training",".","Inherit","this","after","_TestTraining","to","enable","test","cases","for","batch","training","."]
code: def make_vec_env_and_successful_return(self, test, num_envs=2):
      successful_return = self.make_env_and_successful_return(
          test=test
      )[1]
      vec_env = pfrl.envs.SerialVectorEnv(
          [
              self.make_env_and_successful_return(test=test)[0]
              for _ in range(num_envs)
          ]
      )
      return vec_env, successful_return
  
imports: import logging
  import os
  import tempfile
  from unittest import mock
  import numpy
  import pytest
  import pfrl
  from pfrl.experiments import train_agent_async, train_agent_batch_with_evaluation, train_agent_with_evaluation
  from pfrl.experiments.evaluator import batch_run_evaluation_episodes, run_evaluation_episodes
  from pfrl.utils import random_seed
label_desc: Use image node_id 1 for calling the _TestBatchTrainingMixin obj's underlying member method code with example usage: obj.make_vec_env_and_successful_return(test, num_envs) and returns: vec_env,  successful_return