Moviepy slidein and slideout transitions

I'm trying to use slide in and out transitions between videoclips with no luck I was only available to make it work using crossfadein like this:

 from moviepy.editor import VideoFileClip, concatenate_videoclips, vfx, afx, transfx, concatenate, 
 CompositeVideoClip

 delay = 1
 output = "out.mp4"
 clip1 = VideoFileClip("174_3.mp4")
 clip2 = VideoFileClip("174_4.mp4")
 clip3 = VideoFileClip("174_5.mp4")
 clip4 = VideoFileClip("174_6.mp4")


final = concatenate([clip1,
                 clip2.crossfadein(delay),
                 clip3.crossfadein(delay),
                 clip4.crossfadein(delay)],
         padding=-delay, method="compose")
final.write_videofile(output)

But when I use the example on https://github.com/Zulko/moviepy/blob/3d86a2c4cba6769528112765d964eaec273d7636/moviepy/video/compositing/transitions.py

 from moviepy.editor import VideoFileClip, concatenate_videoclips, vfx, afx, transfx, concatenate, 
 CompositeVideoClip

 output = "out.mp4"
 clip1 = VideoFileClip("174_3.mp4")
 clip2 = VideoFileClip("174_4.mp4")
 clip3 = VideoFileClip("174_5.mp4")
 clip4 = VideoFileClip("174_6.mp4")

 clips = [clip1, clip2, clip3, clip4];
 CompositeVideoClip(clips)

 slided_clips = [clip.fx( transfx.slide_out, 1, 'bottom') for clip in clips]
 final_clip = concatenate( slided_clips, padding=-1)
 final_clip.write_videofile(output) 

This result is videos concatenated but not transition at all, please let me know what I'm doing wrong