Shows: `CRITICAL **: ges_clip_move_to_layer: assertion 'GES_IS_LAYER (layer)' failed`

critical.py

import gi
gi.require_version('GES', '1.0')

from gi.repository import GES, Gst, GstPbutils

Gst.init(None)
GES.init()

p = GES.Project.new()
tl = p.extract()

vtrack = GES.VideoTrack.new()
tl.add_track(vtrack)

layer = tl.append_layer()


def add(start):
	clip = GES.TitleClip()
	clip.set_duration(100 * Gst.MSECOND)
	clip.set_start(start)
	layer.add_clip(clip)
	return clip

def a():
	clips = [add(i * Gst.SECOND) for i in range(4)]
	#print (clips)


	group = None
	for clip in clips:
		if not group:
			group = clip
		else:
			group = GES.Container.group([clip, group])

	return clips

for ii in [
		(0,1,2,3), (1,2,3,0), (2,3,0,1),
		(3,0,1,2), (0,2,3,1), (3,2,0,1)]:
	print ()
	print ("Deleting the 4 clips grouped as (3, (2, (1, 0))) in this order:", ii)
	clips = a()
	for i in ii:
		print(i, layer.remove_clip(clips[i]))