Pymongo-提取嵌套结构中键的所有值

Question

嗨，我在mongo中具有以下结构

{
"_id": "233",
"statistics": [
    {
        "lastCommunicationTime": "2019-03-07 03:29:02 AM",
        "statusKey": "1"
    },
    {
        "lastCommunicationTime": "2018-03-07 04:29:02 AM",
        "statusKey": "2"
    },

],
"altitude": "",

}

我正在尝试提取lastCommunicationTime的所有值。我怎么做？我没有找到真正的解决方案

 pipeline = [
            {"$match": {"_id": "233"}},
            {"$project": {"lastCommunicationTime":1}}
             ]
    dd=posts.aggregate(pipeline)