用python修改xml节点后如何保存回xml文件里？

<?xml version="1.0" encoding="utf-8"?>
<config>
    <id>0</id>
    <log_path>E:/Python</log_path>
</config>

from xml.etree import ElementTree
xml_file='config.xml'
xml=ElementTree.ElementTree(file=xml_file).getroot()
xml.find('id').text=1