public static bool IsNotFoundOrImplemented(this Ret.RetStatus status) => status.Code == HttpStatusCode.NotFound || status.Code == HttpStatusCode.NotImplemented;
public static bool IsRedirect(this Ret.RetStatus status) => ((int)status.Code / 100) == 3;
public static bool IsNotFound(this Ret.RetStatus status) => status.Code == HttpStatusCode.NotFound;