public async Task <IEnumerable <Person> > GetFriendsAsync(
     [Parent] Person recipient,
     PersonByIdDataLoader personById,
     CancellationToken cancellationToken)
 {
     return(await personById.LoadAsync(
                recipient.FriendIds, cancellationToken)
            .ConfigureAwait(false));
 }
 public Task <Person> GetPersonByIdAsync(
     Guid id,
     PersonByIdDataLoader personById,
     CancellationToken cancellationToken) =>
 personById.LoadAsync(id, cancellationToken);