Python:如何检查XML字符串是否为有效的XML

import xml.etree.ElementTree as ET

def is_valid_xml(xml_string):
    try:
        ET.fromstring(xml_string)
        return True
    except ET.ParseError:
        return False

from lxml import etree

def is_valid_xml(xml_string):
    try:
        etree.fromstring(xml_string)
        return True
    except etree.XMLSyntaxError:
        return False

import xmlschema

def is_valid_xml(xml_string):
    schema = xmlschema.XMLSchema('<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"></xs:schema>')
    try:
        schema.validate(xml_string)
        return True
    except xmlschema.XMLSchemaValidationError:
        return False