code: def test_default_values(self):
      # Test with missing optional parameters
      result = get_ctm_line(
          source="test_source",
          channel=None,
          start_time=0.123,
          duration=0.456,
          token="word",
          conf=None,
          type_of_token=None,
          speaker=None,
      )
      expected = "test_source 1 0.12 0.46 word NA unknown NA\n"
      assert result == expected, "Failed on default values"
  
imports: import os
  import numpy
  import pytest
  import torch
  from omegaconf import DictConfig
  from nemo.collections.asr.parts.utils.data_simulation_utils import DataAnnotator, SpeechSampler, add_silence_to_alignments, binary_search_alignments, get_cleaned_base_path, get_split_points_in_alignments, normalize_audio, read_noise_manifest
  from nemo.collections.asr.parts.utils.manifest_utils import get_ctm_line
label_desc: Use image node_id 8 for calling the TestGetCtmLine obj's underlying member method code with example usage: obj.test_default_values() without return types