/// <summary>
        /// Adds one or more new custom properties
        /// </summary>
        /// <param name="CustomPropertyList"></param>
        /// <returns></returns>
        public void AddCustomProperty(CustomPropertyList list)
        {
            //build URI to get shapes
            string strURI    = Product.BaseProductUri + "/slides/" + FileName + "/DocumentProperties";///" + slideNumber + "/theme/color-scheme";
            string signedURI = Utils.Sign(strURI);

            string strContent = ToXml(list);

            Stream responseStream = Utils.ProcessCommand(signedURI, "POST", strContent, "xml");
        }
        /// <summary>
        /// Adds one or more new custom properties
        /// </summary>
        /// <param name="CustomPropertyList"></param>
        /// <returns></returns>
        public void AddCustomProperty(CustomPropertyList list)
        {
            //build URI
            string strURI    = Product.BaseProductUri + "/slides/" + FileName + "/presentation/documentProperties";
            string signedURI = Utils.Sign(strURI);

            string strContent = ToXml(list);

            Stream responseStream = Utils.ProcessCommand(signedURI, "POST", strContent, "xml");
        }