xmlDocument.writeToFile('document.xml') is not defined for the type XmlDocument

[Ztagdev]

Hi, I am using this plugin to write XML document, but the code is giving error at this line.

XmlDocument xmlDocument = XmlDocument([
XmlDeclaration(version: '1.0', encoding: 'UTF-8'),
XmlElement(
name: 'root',
children: menu,
),
]);
xmlDocument.writeToFile('document.xml');

This is the version of plugin I am using:

xml_parser: ^0.1.1

Anyone please help me.
Thankx