How to use the moviepy.utils.close_all_clips function in moviepy

def test_duration():

    clip = TextClip('hello world', size=(1280,720), color='white')
    clip = clip.set_duration(5) #  Changed due to #598.
    assert clip.duration == 5
    clip.close()

    clip2 = clip.fx(blink, d_on=1, d_off=1)
    clip2 = clip2.set_duration(5)
    assert clip2.duration == 5
    close_all_clips(locals())

def test_invert_colors():
    clip = get_test_video()
    clip1 = invert_colors(clip)
    clip1.write_videofile(os.path.join(TMP_DIR, "invert_colors1.webm"))
    close_all_clips(locals())

def test_mirror_x():
    clip = get_test_video()
    clip1 = mirror_x(clip)
    clip1.write_videofile(os.path.join(TMP_DIR, "mirror_x1.webm"))
    close_all_clips(locals())

def test_speedx():
    clip = get_test_video()

    clip1 = speedx(clip, factor=0.5)  # 1/2 speed
    assert clip1.duration == 2
    clip1.write_videofile(os.path.join(TMP_DIR, "speedx1.webm"))

    clip2 = speedx(clip, final_duration=2)  # 1/2 speed
    assert clip2.duration == 2
    clip2.write_videofile(os.path.join(TMP_DIR, "speedx2.webm"))

    clip2 = speedx(clip, final_duration=3)  # 1/2 speed
    assert clip2.duration == 3
    clip2.write_videofile(os.path.join(TMP_DIR, "speedx3.webm"))
    close_all_clips(locals())

def test_lum_contrast():
    clip = get_test_video()
    clip1 = lum_contrast(clip)
    clip1.write_videofile(os.path.join(TMP_DIR, "lum_contrast1.webm"))
    close_all_clips(locals())

def test_write_gif_ffmpeg():
    clip = VideoFileClip("media/big_buck_bunny_432_433.webm").subclip(0.2, 0.4)
    location = os.path.join(TMP_DIR, "ffmpeg_gif.gif")
    clip.write_gif(location, program="ffmpeg")
    assert os.path.isfile(location)
    close_all_clips(locals())

def test_save_frame():
    clip = VideoFileClip("media/big_buck_bunny_432_433.webm")
    location = os.path.join(TMP_DIR, "save_frame.png")
    clip.save_frame(location, t=0.5)
    assert os.path.isfile(location)
    close_all_clips(locals())

def test_resize():
    clip = get_test_video()

    clip1 = resize(clip, (460, 720))  # New resolution: (460,720)
    assert clip1.size == (460, 720)
    clip1.write_videofile(os.path.join(TMP_DIR, "resize1.webm"))

    clip2 = resize(clip, 0.6)  # width and heigth multiplied by 0.6
    assert clip2.size == (clip.size[0] * 0.6, clip.size[1] * 0.6)
    clip2.write_videofile(os.path.join(TMP_DIR, "resize2.webm"))

    clip3 = resize(clip, width=800)  # height computed automatically.
    assert clip3.w == 800
    # assert clip3.h == ??
    clip3.write_videofile(os.path.join(TMP_DIR, "resize3.webm"))
    close_all_clips(locals())

def test_write_gif_imageio():
    clip = VideoFileClip("media/big_buck_bunny_432_433.webm").subclip(0.2, 0.8)
    location = os.path.join(TMP_DIR, "imageio_gif.gif")
    clip.write_gif(location, program="imageio")
    assert os.path.isfile(location)
    close_all_clips(locals())

def test_PR_306():

    assert TextClip.list('font') != []
    assert TextClip.list('color') != []

    with pytest.raises(Exception):
         TextClip.list('blah')
    close_all_clips(locals())