Full schema definition example for GraphQL Input Union RFC

schema.graphql

literal PostInputKind
literal ImageInputKind

input AddPostInput {
  kind: ImageInputKind
  title: String!
  body: String!
}

input AddImageInput  {
  kind: PostInputKind
  photo: String!
  caption: String
}

inputUnion AddMediaBlock = AddPostInput | AddImageInput

input EditPostInput {
  inputTypeName: PostInputKind
  title: String
  body: String
}

input EditImageInput {
  inputTypeName: ImageInputKind
  photo: String
  caption: String
}

inputUnion EditMediaBlock = EditPostInput | EditImageInput

type PostBlock {
  title: String
  body: String
}

type ImageBlock {
  photo: String
  caption: String
}

union Content = PostBlock | ImageBlock

type Media {
  id: ID
  content: [Content]
}

type Mutation {
   createMedia(content: [AddMediaBlock]!): Media   
   editMedia(id: ID! content: [EditMediaBlock!]): Media
}