def is_html(ct_headers, url, allow_xhtml=False):
    if not ct_headers:
        return is_html_file_extension(url, allow_xhtml)
    headers = split_header_words(ct_headers)
    if len(headers) < 1:
        return is_html_file_extension(url, allow_xhtml)
    first_header = headers[0]
    first_parameter = first_header[0]
    ct = first_parameter[0]
    html_types = ["text/html"]
    if allow_xhtml:
        html_types += [
            "text/xhtml", "text/xml",
            "application/xml", "application/xhtml+xml",
            ]
    return ct in html_types
ct_headers: Sequence of Content-Type headers
dataset/ETHPy150Open Masood-M/yalih/mechanize/_headersutil.py/is_html