code: def _prepareDummyTrainingData(self):
      tmp_dir = self.get_temp_dir()
      wav_dir = os.path.join(tmp_dir, "wavs")
      os.mkdir(wav_dir)
      self._saveWavFolders(wav_dir, ["a", "b", "c"], 100)
      background_dir = os.path.join(wav_dir, "_background_noise_")
      os.mkdir(background_dir)
      wav_data = self._getWavData()
      for i in range(10):
          file_path = os.path.join(
              background_dir, "background_audio_%d.wav" % i
          )
          self._saveTestWavFile(file_path, wav_data)
      return wav_dir
  
file_path: tensorflow-upstream/tensorflow/examples/speech_commands/train_test.py
imports: import os
  import unittest
  import tensorflow
  from tensorflow.examples.speech_commands import train
  from tensorflow.python.framework import test_util
  from tensorflow.python.platform import gfile
  from tensorflow.python.platform import test
label_desc: Use image node_id 4 for calling the TrainTest obj's underlying member method code with example usage: obj._prepareDummyTrainingData() and returns: wav_dir