如何在python中将xml变量转换为xml文件？

import xml.etree.ElementTree as ET

# 创建XML根节点
root = ET.Element("root")

# 创建子节点
child = ET.SubElement(root, "child")
child.text = "Hello"

# 创建XML树
tree = ET.ElementTree(root)

# 将XML树写入文件
tree.write("output.xml")

xml_string = ET.tostring(root, encoding="utf-8").decode("utf-8")