graphql - @apollo/federation 使用文档中的示例引发错误

Question

在自己尝试解决问题后，我尝试了文档中的示例，但遇到了类似的问题，文档是错误的，还是我在做一些愚蠢的事情？

我要执行的示例是此页面中的示例：https ://www.apollographql.com/docs/apollo-server/federation/introduction/

相关的代码是：

const server = new ApolloServer({
  schema: buildFederatedSchema([{
    typeDefs: gql`
      extend type Query {
        me: User
      }

      type User @key(fields: "id") {
        id: ID!
        username: String!
      }
    `,
    resolvers: [],
  }, {
    typeDefs: gql`
      extend type Query {
        topProducts(first: Int = 5): [Product]
      }

      type Product @key(fields: "upc") {
        upc: String!
        name: String!
        price: Int
      }
    `,
    resolvers: [],
  }, {
    typeDefs: gql`
      type Review {
        body: String
        author: User @provides(fields: "username")
        product: Product
      }

      extend type User @key(fields: "id") {
        id: ID! @external
        reviews: [Review]
      }

      extend type Product @key(fields: "upc") {
        upc: String! @external
        reviews: [Review]
      }
    `,
    resolvers: [],
  }]),
  context: ({ req }) => ({ user: req.user }),
})

请注意，我故意将解析器留空，我只是想编译架构。

这是我得到的错误：

GraphQLSchemaValidationError: Field "User.id" can only be defined once. Field "Product.upc" can only be defined once.

有人可以帮我解决这个问题吗？