如何使用请求库发送xml正文？

def request():
    #encoded_xml = urllib.urlencode({'XML': read_xml()})
    #encoded_xml = read_xml()
    headers = {'Authorization': AUTH_TOKEN,\
               'developerToken': DEVELOPER_TOKEN,\
               'clientCostumerID': CLIENT_ID}
    content = {'__rdxml': encoded_xml}
    #content = encoded_xml
    #content = {'__rdxml': read_xml2()}
    r = requests.post(URL, data=content,\
        headers=headers)
    return r
def request():
    #encoded_xml = urllib.urlenc