I believe that, this code can help you:
from lxml.html.clean import Cleaner
html_text = "<html><head><title>Hello</title><body>Text</body></html>"
cleaner = Cleaner(allow_tags=[''], remove_unknown_tags=False)
cleaned_text = cleaner.clean_html(html_text)
与恶龙缠斗过久,自身亦成为恶龙；凝视深渊过久,深渊将回以凝视…
