const resolvers = {
  Query: {
    // ... like before
  },
  Mutation: {
    // ... like before
  },
  Subscription: {
    publications: {
      // ... like before
    },
    postDeleted: {
      subscribe: (parent, args, ctx, info) => {
        const selectionSet = `{ previousValues { id title } }`
        return ctx.db.subscription.post(
          {
            where: {
              mutation_in: ['DELETED'],
            },
          },
          selectionSet,
        )
      },
      resolve: (payload, args, context, info) => {
        return payload ? payload.post.previousValues : payload
      },
    },
  },
}