code: def test_wave_channel_selection(self):
      signal, sample_rate = load_audio_file(
          stereo_sample_file, channel=1
      )
      self.assertTrue(signal.shape == (182919,))
      self.assertTrue(np.allclose(signal[:4], [38, 36, 34, 31]))
  
imports: from __future__ import absolute_import, division, print_function
  import io
  import unittest
  from os.path import join
  from madmom.io.audio import *
  from .None import AUDIO_PATH, DATA_PATH
label_desc: Use image node_id 4 for calling the TestLoadAudioFileFunction obj's underlying member method code with example usage: obj.test_wave_channel_selection() without return types