/// <summary>
        /// Appends a doctype node to the document.
        /// </summary>
        ///
        /// <param name="name">
        /// The name.
        /// </param>
        /// <param name="fpi">
        /// The formal public identifier
        /// </param>
        /// <param name="uri">
        /// The URI
        /// </param>

        protected override void AppendDoctypeToDocument(string name, string fpi, string uri)
        {
            var doctype = Document.CreateDocumentType(name, "PUBLIC", fpi, uri);

            Document.AppendChildUnsafe(doctype);
        }
        /// <summary>
        /// Appends a doctype node to the document.
        /// </summary>
        ///
        /// <param name="name">
        /// The name.
        /// </param>
        /// <param name="publicIdentifier">
        /// DocType public identifier
        /// </param>
        /// <param name="systemIdentifier">
        /// DocType system identifier.
        /// </param>

        protected override void AppendDoctypeToDocument(string name, string publicIdentifier, string systemIdentifier)
        {
            var doctype = Document.CreateDocumentType(name, publicIdentifier, systemIdentifier);

            Document.AppendChildUnsafe(doctype);
        }