无法在python中将xml文件转换为csv

import xml.etree.ElementTree as ET
import csv

tree = ET.parse('input.xml')
root = tree.getroot()

with open('output.csv', 'w', newline='') as csvfile:
    writer = csv.writer(csvfile)
    
    # 写入表头
    header = []
    for child in root[0]:
        header.append(child.tag)
    writer.writerow(header)
    
    # 写入数据
    for element in root.findall('.//'):
        row = []
        for child in element:
            row.append(child.text)
        writer.writerow(row)