def chat(occupantJID, body):
    """
        Send a private chat message to a user in a MUC room.

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

        @param occupantJID: The Room JID of the other user.
        @type occupantJID: L{JID<twisted.words.protocols.jabber.jid.JID>}
        """
