public new Task <ListMessagesResponse> ExecuteAsync()
            {
                var result = new ListMessagesResponse
                {
                    Messages = GmailUtil.GetFakeGmailMessageList()
                };

                return(Task.FromResult(result));
            }
            public new ListMessagesResponse Execute()
            {
                var result      = new ListMessagesResponse();
                var messageList = GmailUtil.GetFakeGmailMessageList();

                foreach (var message in messageList)
                {
                    result.Messages.Add(message);
                }

                return(result);
            }