human
Complete this python program:
def concatenate_videoclips(clips, method='chain', transition=None, bg_color=None, ismask=False, padding=0):
assistant
#Here is the Python program you requested.

    """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], col=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_pos('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