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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def split_header_words(header_values):
 r"""Parse header values into a list of lists containing key,value pairs. The function knows how to deal with ",", ";" and "=" as well as quoted values after "=". A list of space separated tokens are parsed as if they were separated by ";". If the header_values passed as argument contains multiple values, then they are treated as if they were a single value separated by comma ",". This means that this function is useful for parsing header fields that follow this syntax (BNF as from the HTTP/1.1 specification, but we relax the requirement for tokens). headers = #header header = (token | parameter) *( [";"] (token | parameter)) token = 1*<any CHAR except CTLs or separators> separators = "(" | ")" | "<" | ">" | "@" | "," | ";" | ":" | "\" | <"> | "/" | "[" | "]" | "?" | "=" | "{" | "}" | SP | HT quoted-string = ( <"> *(qdtext | quoted-pair ) <"> ) qdtext = <any TEXT except <">> quoted-pair = "\" CHAR parameter = attribute "=" value attribute = token value = token | quoted-string Each header is represented by a list of key/value pairs. The value for a simple token (not part of a parameter) is None. Syntactically incorrect headers will not necessarily be parsed as you would want. This is easier to describe with some examples: [[('foo', 'bar'), ('port', '80,81'), ('discard', None)], [('bar', 'baz')]] [[('text/html', None), ('charset', 'iso-8859-1')]] [[('Basic', None), ('realm', '"foobar"')]] """

    assert not isinstance(header_values, str)
    result = []
    for text in header_values:
        orig_text = text
        pairs = []
        while text:
            m = HEADER_TOKEN_RE.search(text)
            if m:
                text = unmatched(m)
                name = m.group(1)
                m = HEADER_QUOTED_VALUE_RE.search(text)
                if m:  # quoted value
                    text = unmatched(m)
                    value = m.group(1)
                    value = HEADER_ESCAPE_RE.sub(r"\1", value)
                else:
                    m = HEADER_VALUE_RE.search(text)
                    if m:  # unquoted value
                        text = unmatched(m)
                        value = m.group(1)
                        value = value.rstrip()
                    else:
                        # no value, a lone token
                        value = None
                pairs.append((name, value))
            elif text.lstrip().startswith(","):
                # concatenated headers, as per RFC 2616 section 4.2
                text = text.lstrip()[1:]
                if pairs: result.append(pairs)
                pairs = []
            else:
                # skip junk
                non_junk, nr_junk_chars = re.subn("^[=\s;]*", "", text)
                assert nr_junk_chars > 0, (
                    "split_header_words bug: '%s', '%s', %s" %
                    (orig_text, text, pairs))
                text = non_junk
        if pairs: result.append(pairs)
    return result