Subdocument Operation LookupInAsync must throw PathNotFoundException

static async Task Main(string[] args)

 {

 try

 {

 var cluster = await Couchbase.Cluster.ConnectAsync("couchbase://localhost", "Administrator", "password");

 var bucket = await cluster.BucketAsync("travel-sample");

var scope = await bucket.ScopeAsync("inventory");

var coll = await scope.CollectionAsync("airport");

var key = "airport-500001";

var document = new { id=500001, type = "airport", airportname = "Francis Airport", Country = "France" };

await coll.UpsertAsync<dynamic>(key, document);

var airportDoc = await coll.GetAsync(key);

Console.WriteLine(airportDoc.ContentAs<dynamic>());

var result = await coll.LookupInAsync(key, specs=>specs.Get("some-field-that-doesnt-exist"));

Console.WriteLine("LookupIn Output Is " + result.ContentAs<string>(0)); 

 }

 catch (CouchbaseException ex)

 {

 Console.WriteLine(ex); 

 }

 catch (Exception ex)

 {

 Console.WriteLine(ex); 

 }

 Console.Read();

 }