如果我有一组如下所示的MongoDB文档，我该怎么做才能得到一个只返回拥有2只宠物的家庭的find()结果，这些宠物都喜欢肝脏？这是我期望的工作:db.delegation.find({pets:2,$and:[{'foods.liver':true},{'foods.allLike':true}]})这是文档集:{"_id":ObjectId("5384888e380efca06276cf5e"),"family":"smiths","pets":2,"foods":[{"name":"chicken","allLike":true,},{"name":"liver","allLik