[{linenumber:"car",type:"004",nested:{info:{subinfo:"B"}},},{linenumber:"car",type:"005",nested:{info:{subinfo:"G"}},}]

db.collection.aggregate([{$match:{$and:[{linenumber:"car"},{"nested.info.subinfo":{$in:["B","G"]}}]}},{$group:{_id:null,types:{$addToSet:"$type"}}}])