part	instance	return
Part-tag-1	NULL	NULL
Part-tag-2	NULL	Instance-tag-1 (Left)
Part-tag-2	Instance-tag-1 (Left)	Instance-tag-2 (Right)
Part-tag-2	Instance-tag-2 (Right)	NULL
Part-tag-3	NULL	Instance-tag-3 (Front)
Part-tag-3	Instance-tag-3 (Front)	Instance-tag-4 (Rear)
Part-tag-3	Instance-tag-4 (Rear)	NULL