如何从其他列表中按值删除列表

Question

list = [[5, 5, 5, 5], [6, 6, 6, 6], [6, 8, 9, 7]]
list2 = [[5, 5, 5, 5], [6, 6, 6, 6], [6, 8, 9, 7],[9, 9, 9, 9]]

newlist=list+list2
update=list(dict.fromkeys(newlist))# not hashable
other=newlist-list # not worked

我如何删除重复项只会更新差异。