code: def test_save(self):
      agent = TestAgent(self.alg)
      save_path1 = "model.ckpt"
      save_path2 = os.path.join("my_model", "model-2.ckpt")
      agent.save(save_path1)
      agent.save(save_path2)
      self.assertTrue(os.path.exists(save_path1))
      self.assertTrue(os.path.exists(save_path2))
  
imports: import numpy
  import unittest
  import os
  import torch
  import torch.nn
  import torch.optim
  import parl
label_desc: Use image node_id 3 for calling the ACAgentBaseTest obj's underlying member method code with example usage: obj.test_save() without return types