password: Password used to log on to the server.  May be L{None}.
    @ivar realname: Supplied to the server during login as the "Real name"
        or "ircname".  May be L{None}.
    @ivar username: Supplied to the server during login as the "User name".
        May be L{None}

    @ivar userinfo: Sent in reply to a C{USERINFO} CTCP query.  If L{None}, no
        USERINFO reply will be sent.
        "This is used to transmit a string which is settable by
        the user (and never should be set by the client)."
    @ivar fingerReply: Sent in reply to a C{FINGER} CTCP query.  If L{None}, no
        FINGER reply will be sent.
    @type fingerReply: Callable or String

    @ivar versionName: CTCP VERSION reply, client name.  If L{None}, no VERSION
        reply will be sent.
    @type versionName: C{str}, or None.
    @ivar versionNum: CTCP VERSION reply, client version.
    @type versionNum: C{str}, or None.
    @ivar versionEnv: CTCP VERSION reply, environment the client is running in.
    @type versionEnv: C{str}, or None.

    @ivar sourceURL: CTCP SOURCE reply, a URL where the source code of this
        client may be found.  If L{None}, no SOURCE reply will be sent.

    @ivar lineRate: Minimum delay between lines sent to the server.  If
        L{None}, no delay will be imposed.
    @type lineRate: Number of Seconds.

    @ivar motd: Either L{None} or, between receipt of I{RPL_MOTDSTART} and
        I{RPL_ENDOFMOTD}, a L{list} of L{str}, each of which is the content
        of an I{RPL_MOTD} message.

    @ivar erroneousNickFallback: Default nickname assigned when an unregistered
        client triggers an C{ERR_ERRONEUSNICKNAME} while trying to register
        with an illegal nickname.
    @type erroneousNickFallback: C{str}

    @ivar _registered: Whether or not the user is registered. It becomes True
        once a welcome has been received from the server.
    @type _registered: C{bool}

    @ivar _attemptedNick: The nickname that will try to get registered. It may
        change if it is illegal or already taken. L{nickname} becomes the
        L{_attemptedNick} that is successfully registered.
    @type _attemptedNick:  C{str}

    @type supported: L{ServerSupportedFeatures}
    @ivar supported: Available ISUPPORT features on the server

    @type hostname: C{str}
    @ivar hostname: Host name of the IRC server the client is connected to.
        Initially the host name is L{None} and later is set to the host name
        from which the I{RPL_WELCOME} message is received.

    @type _heartbeat: L{task.LoopingCall}
    @ivar _heartbeat: Looping call to perform the keepalive by calling
        L{IRCClient._sendHeartbeat} every L{heartbeatInterval} seconds, or
        L{None} if there is no heartbeat.

    @type heartbeatInterval: C{float}
    @ivar heartbeatInterval: Interval, in seconds, to send I{PING} messages to
        the server as a form of keepalive, defaults to 120 seconds. Use L{None}
        to disable the heartbeat.
    NZ