def keep_clean
      synchronize do
        @read_waiter.delete_unless_alive.each do |e|
          e.signal
        end
        @take_waiter.delete_unless_alive.each do |e|
          e.signal
        end
        @notify_waiter.delete_unless_alive.each do |e|
          e.notify(['close'])
        end
        @bag.delete_unless_alive.each do |e|
          notify_event('delete', e.value)
        end
      end
    end
def keep_clean
      synchronize do
        @read_waiter.delete_unless_alive.each do |e|
          e.signal
        end
        @take_waiter.delete_unless_alive.each do |e|
          e.signal
        end
        @notify_waiter.delete_unless_alive.each do |e|
          e.notify(['close'])
        end
        @bag.delete_unless_alive.each do |e|
          notify_event('delete', e.value)
        end
      end
    end
Removes dead tuples.