code: def test_substitute(self):
      for _ in range(10):
          aug = naa.SpeedAug(stateless=False)
          augmented_data = aug.augment(self.audio)
          augmented_audio = augmented_data[0]
  
          if aug.aug_factor < 1:
              self.assertGreater(len(augmented_audio), len(self.audio))
          else:
              self.assertLess(len(augmented_audio), len(self.audio))
  
file_path: nlpaug/test/augmenter/audio/test_speed.py
imports: import unittest
  import os
  from dotenv import load_dotenv
  import nlpaug.augmenter.audio
  from nlpaug.util import AudioLoader
label_desc: Use image node_id 2 for calling the TestSpeed obj's underlying member method code with example usage: obj.test_substitute() without return types