docs: def subscribe(self, connection, destination):
          """
          Subscribes a connection to the specified destination (topic or queue). 
  
          @param connection: The connection to subscribe.
          @type connection: L{coilmq.server.StompConnection}
  
          @param destination: The topic/queue destination (e.g. '/queue/foo')
          @type destination: C{str} 
          """
          self.log.debug("Subscribing %s to %s" % (connection, destination))
          self._queues[destination].add(connection)
          self._send_backlog(connection, destination)