{
    "_id": "590ad2c78eb79d16bde4a15d",
    "user": "yejia@qq.com",
    "password": "111111",
    "__v": 0,
    "lists": [
      {
        "_id": "590ad2d78eb79d16bde4a15e",
        "update_at": "2017-05-04T07:05:52.174Z",
        "create_at": "2017-05-04T07:05:52.174Z",
        "title": "测试1",
        "isChecked": [
          false
        ],
        "details": [
          "未完"
        ]
      },
      {
        "_id": "590ad3398eb79d16bde4a15f",
        "update_at": "2017-05-04T07:07:28.784Z",
        "create_at": "2017-05-04T07:07:28.784Z",
        "title": "测试2",
        "isChecked": [
          false,
          false
        ],
        "details": [
          "1232",
          "333"
        ]
      }
    ]
  }

像這個例子，如果我要根據子文檔的id："_id": "590ad2d78eb79d16bde4a15e"查找子文檔，該怎麼操作？說明一下，直接用id查詢我會，我不懂的是用子文檔的id查詢子文檔。