code: def test_no_truncate(self):
      with self.assertRaises(ValueError):
          testing_utils.train_model(
              Opt({**_DEFAULT_OPTIONS, **{"truncate": -1}})
          )
  
imports: from parlai.core.opt import Opt
  from parlai.tasks.integration_tests.agents import NUM_TEST, EXAMPLE_SIZE
  from parlai.utils.conversations import Conversations
  import parlai.utils.testing
  import os
  from typing import Dict, Any
  import unittest
label_desc: Use image node_id 2 for calling the TestDynamicBatching obj's underlying member method code with example usage: obj.test_no_truncate() without return types