以下のようなデータがあったとして { "_id" : ObjectId("5f6a3919a761753bb5e73c68"), "author" : "aaa", "question" : "test1", "answers" : [ { "voters" : [ "ccc" ], "_id" : ObjectId("5f6a3919a761753bb5e73c69"), "title" : "a" }, { "voters" : [ "b…