code: def test_save_withignore(self):
      o = Opt({"a": 3, "b": "foo", "override": {"a": 3}})
      with testing_utils.tempdir() as tmpdir:
          fn = os.path.join(tmpdir, "opt")
          o.save(fn)
          o2 = Opt.load(fn)
          assert o != o2
          assert "override" not in o2
  
imports: import json
  import os
  import unittest
  import parlai.utils.testing
  from parlai.core.agents import create_agent_from_opt_file
  from parlai.core.opt import Opt
  from parlai.core.params import ParlaiParser
  from parlai.scripts.compare_opts import compare_opts
label_desc: Use image node_id 2 for calling the TestOpt obj's underlying member method code with example usage: obj.test_save_withignore() without return types