在mongodb中更改嵌入式文档中的根

如何解决在mongodb中更改嵌入式文档中的根

下面是我的输出：

 [
        {
            "_id": "5f637432c57a7d0017af1421","project": [
                {
                    "_id": "5f637774c57a7d0017af1423","projectName": "Notification project","licenseType": "agricultural and biological engineering","location": "chennai","description": "Sample data Sample data Sample data Sample data Sample data.","duration": 70,"createdAt": "2020-09-17T14:49:24.860Z","updatedAt": "2020-09-17T14:49:24.860Z","__v": 0
                },{
                    "_id": "5f63965166bca1001783fbb4","projectName": "Sample project 1","licenseType": "civil","description": "Sample data 1","duration": 30,"createdAt": "2020-09-18T17:01:05.929Z","updatedAt": "2020-09-18T17:01:05.929Z",{
                    "_id": "5f63967866bca1001783fbb9","projectName": "Sample project 2","licenseType": "nuclear","description": "Sample data 2","duration": 80,"createdAt": "2020-09-18T17:01:44.375Z","updatedAt": "2020-09-18T17:01:44.375Z","__v": 0
                }
            ]
        }
    ]

我只想将项目作为新的根目录。我尝试了$ replaceRoot，但是它不起作用。它说它需要一个对象，但是它接收一个字符串。也许我做的方法不正确。

注意：我使用了聚合框架来获得上面显示的输出。

感谢任何帮助！谢谢。