def list_style_image(token, base_url):
    """``list-style-image`` property validation."""
    if get_keyword(token) == 'none':
        return 'none', None
    parsed_url = get_url(token, base_url)
    if parsed_url:
        if parsed_url[0] == 'url' and parsed_url[1][0] == 'external':
            return 'url', parsed_url[1][1]
``list-style-image`` property validation.
weasyprint/css/validation/properties.py