我有收款账户:{"_id":ObjectId("571a0e145d29024733793cfe"),"name":"Cash","user":ObjectId("571a0e145d29024733793cfc")}和交易。事务可以有不同的字段:{"_id":ObjectId("571a0e145d29024733793d06"),"amount":100,"type":"earned","account":ObjectId("571a0e145d29024733793cfe"),"user":ObjectId("571a0e145d29024733793cfc"),},{"_id"