def choice(self, queues, connection):
raise NotImplementedError<EOL>
Choose which queue to select for messages to specified connection.

@param queues: A C{dict} mapping queue name to queues (sets of frames) to which 
                specified connection is subscribed.
@type queues:  C{dict} of C{str} to C{set} of L{stompclient.frame.Frame}

@param connection: The connection that is going to be delivered the frame(s).
@type connection: L{coilmq.server.StompConnection}

@return: A selected queue destination (name) or None if queues C{dict} is empty.
@rtype: C{str}