public override void Invoke(AWSCredentials creds, RegionEndpoint region, int maxItems)
        {
            AmazonShieldConfig config = new AmazonShieldConfig();

            config.RegionEndpoint = region;
            ConfigureClient(config);
            AmazonShieldClient client = new AmazonShieldClient(creds, config);

            ListProtectionGroupsResponse resp = new ListProtectionGroupsResponse();

            do
            {
                ListProtectionGroupsRequest req = new ListProtectionGroupsRequest
                {
                    NextToken = resp.NextToken
                    ,
                    MaxResults = maxItems
                };

                resp = client.ListProtectionGroups(req);
                CheckError(resp.HttpStatusCode, "200");

                foreach (var obj in resp.ProtectionGroups)
                {
                    AddObject(obj);
                }
            }while (!string.IsNullOrEmpty(resp.NextToken));
        }