Typescript type { [k in string]: StuffItem } for NestJS GraphQL

Question

I am trying to find out how to use { [k in string]: StuffItem } type in typescript in GraphQL in NestJS.

StuffItem:

export class StuffItem{
  name: string;
  price: number;
}

We already use { [k in string]: StuffItem } in our RestAPI, with the response like:

{
  "order": {
    "items": {
      "5": { "name":"xxx", "price": 10 }
    }
  }
}

How should we decorate items in Order class to allow the same result?

@ObjectType
export class Order{
  @Field(type => ???)
  items: { [k in string]: StuffItem }
}

Thank you!