Mongodb目前不支持aggregate操作嘛？

我看了[Mongodb dataX](https://github.com/alibaba/DataX/blob/master/mongodbreader/doc/mongodbreader.md)似乎没看到`aggregate`操作相关的说明，请问我想做`aggregate`操作改怎么写配置文件？

Start with the linked mongodbreader/doc/mongodbreader.md documentation and inspect the MongoDB reader's configuration entry point. Determine whether aggregation is supported and where its configuration would be defined; done means documenting a valid configuration or clearly identifying the missing implementation scope.

Written by the indexing model from the issue text.