Mongodb 删除嵌套文档数组中的嵌入文档

我的模式如下所示:

"content" : [
        {
            "_id" : ObjectId("4fc63de85b20fb72290000f8"),
            "assets" : [
                {
                    "path" : "temp/4f840af9565832fa14000002/4f840b1e565832fa14000007/4fc63de85b20fb72290000f7/content/I_Understanding_and_Measuring.pdf",
                    "_id" : ObjectId("4fc63def5b20fb722900010e")
                },
                {
                    "path" : "temp/4f840af9565832fa14000002/4f840b1e565832fa14000007/4fc63de85b20fb72290000f7/content/me.jpg",
                    "_id" : ObjectId("4fc63e4d5b20fb722900015d")
                }
            ],
            "content" : "",
            "name" : "Downloads"
        },
        {
            "_id" : ObjectId("4fc63dfd5b20fb722900012a"),
            "assets" : [
                {
                    "path" : "temp/4f840af9565832fa14000002/4f840b1e565832fa14000007/4fc63de85b20fb72290000f7/content/me.jpg",
                    "_id" : ObjectId("4fc63e055b20fb7229000147")
                },
                {
                    "path" : "temp/4f840af9565832fa14000002/4f840b1e565832fa14000007/4fc63de85b20fb72290000f7/content/thierry-henry-12-31-11-1.jpg",
                    "_id" : ObjectId("4fc63e525b20fb7229000164")
                }
            ],
            "content" : "",
            "name" : "Bio"
        }
    ],

我可以通过以下方式检索此文档:

db.presentations.find({'content.assets._id': ObjectId('4fc63def5b20fb722900010e')})`

我try 了以下方法从assets资源 集合中删除一个文档，但没有成功:

db.presentations.update(
  {'content.assets._id': ObjectId('4fc63def5b20fb722900010e')}, 
  {$pull: {'content.assets': {'_id': ObjectId('4fc63def5b20fb722900010e')}}}
)

我正试图从相应的assets个系列中删除一个项目的id.有什么 idea 吗？