code: def test_choose_channel(self):
      signal, sample_rate = load_audio_file(
          flac_file, sample_rate=22050, num_channels=1, channel=0
      )
      # avconv results in a different length of 91450 samples
      self.assertTrue(np.allclose(len(signal), 91460, atol=10))
      self.assertTrue(
          np.allclose(signal[:5], [34, 32, 37, 35, 32], atol=1)
      )
  
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 9 for calling the TestLoadAudioFileFunction obj's underlying member method code with example usage: obj.test_choose_channel() without return types