code: def test_msc_ltm_mutator(self):
      from parlai.tasks.msc.mutators import LongTermMemoryMutator
  
      ex1, ex2, ex3, ex4 = self._apply_mutator(LongTermMemoryMutator)
  
      assert (
          ex1["labels"]
          == ex2["labels"]
          == ex3["labels"]
          == ex4["labels"]
          == ["personal_knowledge"]
      )
  
imports: import unittest
  from parlai.core.params import ParlaiParser
  from parlai.core.opt import Opt
  from parlai.core.teachers import create_task_agent_from_taskname
  from parlai.core.message import Message
label_desc: Use image node_id 14 for calling the TestSpecificMutators obj's underlying member method code with example usage: obj.test_msc_ltm_mutator() without return types