'Transform an option description into RST nodes.'

def parse_signature(self, sig, signode):

    count = 0
    firstname = ''
    for m in option_desc_re.finditer(sig):
        (optname, args) = m.groups()
        if count:
            signode += addnodes.desc_addname(',    ', ',    ')
        signode += addnodes.desc_name(optname, optname)
        signode += addnodes.desc_addname(args, args)
        if (not count):
            firstname = optname
        count += 1
    if (not firstname):
        raise ValueError
    return firstname
