async def token(bot, user, token=None, *args):
    """
    usage: !token [token]

    Display token explanation. If none is provided, display token list.
    """
    try:
        return bot.token[token]
    except KeyError:
        msg = "usage: !token [token]\ntokens: {}".format(
            ", ".join(bot.token.keys())
        )
        return msg