SimpleSchema的Meteor导入不工作

我正在尝试使用导入来访问对象，但在逻辑上遇到了困难：

schemas.js：

import { SimpleSchema } from 'meteor/aldeed:simple-schema';
export default UsersExtraSchema = new SimpleSchema({
    ...
}

seed.js：

import '/imports/startup/server/schemas.js';
export default class SeedDB {

    loadBaseData() {
        ....
        UsersExtraSchema.validate(attr);
        ...
    }
}

我得到一个错误：

TypeError: Object [object Object] has no method 'validate'
at SeedDB.loadBaseData (imports/startup/server/seed.js:19:26)
at server/main.js:11:14
at /tidee/app/tidee-meteor/.meteor/local/build/programs/server/boot.js:290:5
Exited with code: 8
Your application is crashing. Waiting for file change.

---

你为什么不这样进口

import UsersExtraSchema from '/imports/startup/server/schemas.js';