def shutdown_publisher(publisher)
      begin
        @master.unregister_publisher(publisher.topic_name)
      ensure
        @publishers.delete(publisher) do |pub|
          raise "publisher not found"
        end
        publisher.close
      end
    end
def shutdown_publisher(publisher)
      begin
        @master.unregister_publisher(publisher.topic_name)
      ensure
        @publishers.delete(publisher) do |pub|
          raise "publisher not found"
        end
        publisher.close
      end
    end
shutdown a publisher.
 @param [Publisher] publisher Publisher to be shutdown