def nick(roomJID, nick):
    """
        Change an entity's nick name in a MUC room.

        See: http://xmpp.org/extensions/xep-0045.html#changenick

        @param roomJID: The JID of the room, i.e. without a resource.
        @type roomJID: L{JID<twisted.words.protocols.jabber.jid.JID>}

        @param nick: The new nick name within the room.
        @type nick: C{unicode}
        """
