如何在使用ElementTree (python)解析xml时删除无效字符

I'm trying to import a folder of ~15,000 xml files to a mongo db using python, specifically ElementTree. There seems to be an invalid character in about 5% of the files, mostly &. Document enconding is "ISO-8859-1" and the encoding is declared in the xml files.I'm trying to import a folder of ~15,000 xml fi