code: import numpy as np
  
  from moviepy.audio.AudioClip import CompositeAudioClip
  from moviepy.tools import deprecated_version_of
  from moviepy.video.compositing.CompositeVideoClip import CompositeVideoClip
  from moviepy.video.compositing.on_color import on_color
  from moviepy.video.VideoClip import ColorClip, VideoClip
  
  try:               # Python 2
     reduce
  except NameError:  # Python 3
     from functools import reduce
  
  
  
  def concatenate_videoclips(clips, method="chain", transition=None,
                             bg_color=None, ismask=False, padding = 0):
      """ Concatenates several video clips
  
      Returns a video clip made by clip by concatenating several video clips.
      (Concatenated means that they will be played one after another).
  
      There are two methods:
  
      - method="chain": will produce a clip that simply outputs
        the frames of the succesive clips, without any correction if they are
        not of the same size of anything. If none of the clips have masks the
        resulting clip has no mask, else the mask is a concatenation of masks
        (using completely opaque for clips that don't have masks, obviously).
        If you have clips of different size and you want to write directly the
        result of the concatenation to a file, use the method "compose" instead.
  
      - method="compose", if the clips do not have the same
        resolution, the final resolution will be such that no clip has
         to be resized.
         As a consequence the final clip has the height of the highest
         clip and the width of the widest clip of the list. All the
         clips with smaller dimensions will appear centered. The border
         will be transparent if mask=True, else it will be of the
         color specified by ``bg_color``.
  
      The clip with the highest FPS will be the FPS of the result clip.
  
      Parameters
      -----------
      clips
        A list of video clips which must all have their ``duration``
        attributes set.
      method
        "chain" or "compose": see above.
      transition
        A clip that will be played between each two clips of the list.
  
      bg_color
        Only for method='compose'. Color of the background.
        Set to None for a transparent clip
  
      padding
        Only for method='compose'. Duration during two consecutive clips.
        Note that for negative padding, a clip will partly play at the same
        time as the clip it follows (negative padding is cool for clips who fade
        in on one another). A non-null padding automatically sets the method to
        `compose`.
  
      """
  
      if transition is not None:
          l = [[v, transition] for v in clips[:-1]]
          clips = reduce(lambda x, y: x + y, l) + [clips[-1]]
          transition = None
  
      tt = np.cumsum([0] + [c.duration for c in clips])
  
      sizes = [v.size for v in clips]
  
      w = max([r[0] for r in sizes])
      h = max([r[1] for r in sizes])
  
      tt = np.maximum(0, tt + padding*np.arange(len(tt)))
  
      if method == "chain":
          def make_frame(t):
              i = max([i for i, e in enumerate(tt) if e <= t])
              return clips[i].get_frame(t - tt[i])
  
          def get_mask(c):
              mask = c.mask or ColorClip([1, 1], color=1, ismask=True)
              if mask.duration is None:
                 mask.duration = c.duration
              return mask
  
          result = VideoClip(ismask = ismask, make_frame = make_frame)
          if any([c.mask is not None for c in clips]):
              masks = [get_mask(c) for c in clips]
              result.mask = concatenate_videoclips(masks, method="chain",
                                                   ismask=True)
              result.clips = clips
      elif method == "compose":
          result = CompositeVideoClip( [c.set_start(t).set_position('center')
                                  for (c, t) in zip(clips, tt)],
                 size = (w, h), bg_color=bg_color, ismask=ismask)
      else:
          raise Exception("Moviepy Error: The 'method' argument of "
                          "concatenate_videoclips must be 'chain' or 'compose'")
  
      result.tt = tt
  
      result.start_times = tt[:-1]
      result.start, result.duration, result.end = 0, tt[-1] , tt[-1]
  
      audio_t = [(c.audio,t) for c,t in zip(clips,tt) if c.audio is not None]
      if len(audio_t)>0:
          result.audio = CompositeAudioClip([a.set_start(t)
                                  for a,t in audio_t])
  
      fpss = [c.fps for c in clips if hasattr(c,'fps') and c.fps is not None]
      if len(fpss) == 0:
          result.fps = None
      else:
          result.fps = max(fpss)
  
      return result
  
  
  concatenate = deprecated_version_of(concatenate_videoclips,
                                      oldname="concatenate")
  
apis: numpy.cumsum