query SelectionOfUnion {
  pet1
  pet2
  pet3
  pet4
  pet5
  pet6
}

type Query {
  pet1: CatOrDog
  pet2: CatOrDog!
  pet3: [CatOrDog]
  pet4: [CatOrDog!]
  pet5: [CatOrDog]!
  pet6: [CatOrDog!]!
}

type Cat {
  id: String!
}

type Dog {
  id: String!
}

union CatOrDog = Cat | Dog