'Attempt to set the topic of the given channel, or ask what it is.
If topic is None, then I sent a topic query instead of trying to set the
topic. The server should respond with a TOPIC message containing the
current topic of the given channel.
@type channel: C{str}
@param channel: The name of the channel to change the topic on. If it
has no prefix, C{\'#\'} will be prepended to it.
@type topic: C{str}
@param topic: If specified, what to set the topic to.'

def topic(self, channel, topic=None):

    if (channel[0] not in CHANNEL_PREFIXES):
        channel = ('#' + channel)
    if (topic != None):
        self.sendLine(('TOPIC    %s    :%s' % (channel, topic)))
    else:
        self.sendLine(('TOPIC    %s' % (channel,)))
