https://grantnorwood.com/nullability-in-graphql/

VacationRental-final-schema.graphql

type Query {
  vacationRentalById(id: $id) : VacationRental
}
 
type VacationRental {
  id: ID!
  title: String
  description: String
  owner: Owner!
  roomCount: Int
  address: Address
  geolocation: GeoLocation
  price: Price
}
 
type Owner {
  name: String!
  email: String!
  phone: String!
  twitterHandle: String
  inboxNotifications: [Notification]
}
 
type Address {
  line1: String!
  line2: String
  city: String!
  state: String!
  zip: String!
}
 
type Price {
  amount: Float!
  currency: String!
}
 
type GeoLocation {
  latitude: String!
  longitude: String!
}
 
type Notification {
  timestamp: String!
  message: String!
}