def shutdown
      return unless @finalizer && @subject.respond_to?(@finalizer, true)

      task(:finalizer, @finalizer, { call: @finalizer, subject: @subject },
           dangerous_suspend: true, &Cell.shutdown)
    end
def shutdown
      return unless @finalizer && @subject.respond_to?(@finalizer, true)

      task(:finalizer, @finalizer, { call: @finalizer, subject: @subject },
           dangerous_suspend: true, &Cell.shutdown)
    end
Run the user-defined finalizer, if one is set