/// <summary>
        /// Validate the field passed in
        /// </summary>
        /// <param name="document"></param>
        /// <param name="node"></param>
        /// <param name="useRelative"></param>
        private static HtmlNode ValidateDefaults(HtmlDocument document, HtmlNode node, bool useRelative)
        {
            document = document.NotNull();

            if (useRelative)
            {
                node = node.NotNull();
            }

            return useRelative ? node : document.DocumentNode;
        }