code: public void unsubscribe( String name, Map header ) {
      if (header == null) header = new HashMap();
      synchronized( _listeners ) { _listeners.remove( name ); }
      header.put( "destination", name );
      transmit( Command.UNSUBSCRIBE, header );
    }
docs: Unsubscribe from a channel.  Automatically unregisters all
  listeners of the channel.  To re-subscribe with listeners,
  subscribe must be passed the listeners again.
  
  @param name The name of the channel to unsubscribe from.
  @param header Additional headers to send to the server.