def __clean(s):

        s = s.lstrip('*')

        s = s.lstrip('.')

        if s.find('[') != -1:

            exts = []

            start, stop = s.find('['), s.find(']')

            for suffix in s[start + 1:stop]:

                exts.append(s[:s.find('[')] + suffix)

            return map(lower, exts)

        else:

            return map(lower, [s])

    for lx, t in sorted(lexers.LEXERS.items()):

        m = map(__clean, t[-2])

        if m:

            m = reduce(lambda x, y: x + y, m)

            for ext in m:

                desc = lx.replace('Lexer', '')

                d[ext].append(desc)

    return dict(d)

def get_index_filenames():

    """

    Get list of known indexable filenames from pygment lexer internals

    """

    filenames = []

    def likely_filename(s):

        return s.find('*') == -1 and s.find('[') == -1

    for lx, t in sorted(lexers.LEXERS.items()):

        for f in ifilter(likely_filename, t[-2]):

            filenames.append(f)

    return filenames

def get_custom_lexer(extension):

    """

    returns a custom lexer if it's defined in rcextensions module, or None

    if there's no custom lexer defined

    """

    import kallithea