我安装了passport-local-mongoose包，当我使用这个：

const mongoose = require("mongoose");
const plm = require("passport-local-mongoose");

mongoose.connect(
  `mongodb+srv://Funn:[email protected]/`, 
   {
    dbName: "Auth"
   }

).then((c) => console.log("db connected",c.connection.host))
  .catch((e) => console.log(e));
  
   const userSchema = {
   username: String,
   password: String,
   secret:String,
  }

userSchema.plugin(plm);// because of this line it throw error 

module.exports = mongoose.model("user", userSchema);

字符串
它抛出一个错误：

userSchema.plugin is not a function

型