如何检查XML中是否存在节点？

import xml.dom.minidom

def check_xml_node(xml_string, node_name):
    dom = xml.dom.minidom.parseString(xml_string)
    nodes = dom.getElementsByTagName(node_name)
    if len(nodes) > 0:
        return True
    else:
        return False

import xml.etree.ElementTree as ET

def check_xml_node(xml_string, node_name):
    root = ET.fromstring(xml_string)
    nodes = root.findall(".//{}".format(node_name))
    if len(nodes) > 0:
        return True
    else:
        return False