IonicModule.forRoot on Ionic v4

Ionic v3 documentation says IonicModule.forRoot function can have two different arguments 1. root Component and config (optional) (

While running ionic V4 project, by default there is no value passed on forRoot static function, I have found only config can be passed, when I try to pass ‘Platforms’ its throwing an error

Object literal may only specify known properties, and 'platforms' does not exist in type 'IonicConfig'. [2345]

Any replacement for Platforms?