code: def test_multiply_stereo_volume():
      clip = AudioFileClip("media/crunching.mp3")
  
      # stereo mute
      clip_left_channel_muted = multiply_stereo_volume(clip, left=0)
      clip_right_channel_muted = multiply_stereo_volume(
          clip, right=0, left=2
      )
  
      left_channel_muted = clip_left_channel_muted.to_soundarray()[:, 0]
      right_channel_muted = clip_right_channel_muted.to_soundarray()[
          :, 1
      ]
  
      z_channel = np.zeros(len(left_channel_muted))
  
      assert np.array_equal(left_channel_muted, z_channel)
      assert np.array_equal(right_channel_muted, z_channel)
  
      # stereo level doubled
      left_channel_doubled = clip_right_channel_muted.to_soundarray()[
          :, 0
      ]
      expected_left_channel_doubled = clip.to_soundarray()[:, 0] * 2
      assert np.array_equal(
          left_channel_doubled, expected_left_channel_doubled
      )
  
      # mono muted
      sinus_wave = lambda t: [np.sin(440 * 2 * np.pi * t)]
      mono_clip = AudioClip(sinus_wave, duration=1, fps=22050)
      muted_mono_clip = multiply_stereo_volume(mono_clip, left=0)
      mono_channel_muted = muted_mono_clip.to_soundarray()
  
      z_channel = np.zeros(len(mono_channel_muted))
      assert np.array_equal(mono_channel_muted, z_channel)
  
      # mono doubled
      mono_clip = AudioClip(sinus_wave, duration=1, fps=22050)
      doubled_mono_clip = multiply_stereo_volume(
          mono_clip, left=None, right=2
      )  # using right
      mono_channel_doubled = doubled_mono_clip.to_soundarray()
      d_channel = mono_clip.to_soundarray() * 2
      assert np.array_equal(mono_channel_doubled, d_channel)
  
imports: import decimal
  import importlib
  import math
  import numbers
  import os
  import random
  import sys
  import numpy
  import pytest
  from moviepy import AudioClip, AudioFileClip, BitmapClip, ColorClip, VideoClip, VideoFileClip
  from moviepy.audio.fx import audio_delay, audio_fadein, audio_fadeout, audio_normalize, multiply_stereo_volume, multiply_volume
  from moviepy.tools import convert_to_seconds
  from moviepy.video.fx import blackwhite, crop, even_size, fadein, fadeout, freeze, freeze_region, invert_colors, loop, lum_contrast, make_loopable, margin, mask_and, mask_or, mirror_x, mirror_y, multiply_color, multiply_speed, resize, rotate, time_mirror, time_symmetrize
label_desc: Use image node_id 37 for calling a global function with example usage: test_multiply_stereo_volume() without return types