class_docstr: Kaldi dir meta data IO test
docstr: test custom properties  
code: def test_property(self):
      """test custom properties"""
      utt = kaldi_dir.Utt()
      self.assertIsNone(utt.wavlen)
      utt.wavlen = 1
      self.assertEqual(utt.wavlen, 1)
  
file_path: delta/delta/utils/kaldi/kaldi_dir_test.py
imports: import os
  from absl import logging
  import delta.compat
  from delta.utils.kaldi import kaldi_dir
  from delta.utils.kaldi.kaldi_dir_utils import gen_dummy_meta
label_desc: Use image node_id 3 for calling the KaldiDirTest obj's underlying member method code with example usage: obj.test_property() without return types