Improving TypeScript Schema Design for API Validation and Transformation

typescript 
const Region = Schema.Struct({
  id: Schema.NonEmptyTrimmedString
});

const Country = Schema.Struct({
  id: Schema.NonEmptyTrimmedString,
  region: Schema.optionalWith(Region, {as: "Option"})
});

const City = Schema.Struct({
  id: Schema.NonEmptyTrimmedString,
  country: Schema.optionalWith(Country, {as: "Option"})
});

 typescript
const RegionDTO = Schema.Struct({
  id: Schema.NonEmptyTrimmedString
});

const CountryDTO = 
Schema.Struct({
  id: Schema.NonEmptyTrimmedString,
  region: Schema.optionalWith(Schema.NonEmptyString) // this is the id of the Region
});
...etc...same logic goes for city

typescript 
const dto2City = Schema.transformOrFail(CityDTO, City, {strict: true, decode:(dto...)=>..., encode(city..)=>...})