'Join a channel.
@type channel: C{str}
@param channel: The name of the channel to join. If it has no prefix,
C{\'#\'} will be prepended to it.
@type key: C{str}
@param key: If specified, the key used to join the channel.'

def join(self, channel, key=None):

    if (channel[0] not in CHANNEL_PREFIXES):
        channel = ('#' + channel)
    if key:
        self.sendLine(('JOIN    %s    %s' % (channel, key)))
    else:
        self.sendLine(('JOIN    %s' % (channel,)))
