Extract from the given iterable of lines the list of words.

    :param lines: an iterable of lines;
    :return: a generator of words of lines.

def extract_words(lines):
    """
    Extract from the given iterable of lines the list of words.

    :param lines: an iterable of lines;
    :return: a generator of words of lines.
    """
    for line in lines:
        for word in re.findall(r"\w+", line):
            yield word