docs: public static String addDocBookPreamble(final DocBookVersion docBookVersion, final String xml, final String elementName,
              final String entityName) {
          if (docBookVersion == DocBookVersion.DOCBOOK_50) {
              final String xmlWithNamespace = DocBookUtilities.addDocBook50Namespace(xml, elementName);
              return XMLUtilities.addDoctype(xmlWithNamespace, elementName, entityName);
          } else {
              return DocBookUtilities.addDocBook45Doctype(xml, entityName, elementName);
          }
      }