docs: public BaseTemplate xmlDeclaration() throws IOException {
          out.write("<?xml ");
          writeAttribute("version", "1.0");
          if (configuration.getDeclarationEncoding() != null) {
              writeAttribute(" encoding", configuration.getDeclarationEncoding());
          }
          out.write("?>");
          out.write(configuration.getNewLineString());
          return this;
      }