code: def test_channel_choice(self):
      signal, sample_rate = load_wave_file(
          stereo_sample_file, channel=0
      )
      self.assertTrue(signal.shape == (182919,))
      self.assertTrue(np.allclose(signal[:4], [33, 35, 29, 36]))
      signal, sample_rate = load_wave_file(
          stereo_sample_file, channel=1
      )
      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 6 for calling the TestLoadWaveFileFunction obj's underlying member method code with example usage: obj.test_channel_choice() without return types