我有以下结构的集合。其中有一些重复的内容标题名称和值。但我需要获取确切的文档。{"_id":ObjectId("573ebc7bbf50112d55c0b763"),"topic":"AAA","contents":[{"headerName":"StartYear","value":1995},{"headerName":"Program","value":"AAA"}]},{"_id":ObjectId("573ebc7bbf50112d55c0b763"),"topic":"BBB","contents":[{"headerName":"StartYear","value":19