Facebook 登录，如何获取token_for_business字段

在FaceBook登录中可以通过设置fields指定想要获取的字段，现在在setting中使用以下两种方法指定，都没有生效。

```Swfit

let settings = ["fields": ["id","name","picture","token_for_business","email"]]
let settings1 = ["fields": "id,name,picture,token_for_business,email"]
```