def install(html=False):
    """
    Install doctestcompare for all future doctests.

    If html is true, then by default the HTML parser will be used;
    otherwise the XML parser is used.
    """
    if html:
        doctest.OutputChecker = LHTMLOutputChecker
    else:
        doctest.OutputChecker = LXMLOutputChecker

    Install doctestcompare for all future doctests.

    If html is true, then by default the HTML parser will be used;
    otherwise the XML parser is used.
    
stackoverflow/venv/lib/python3.6/site-packages/lxml/doctestcompare.py