def defer(callable, trans_event, *data)
      async_call = AsyncCall.new(machine, callable, trans_event, *data)
      callback_queue.start unless callback_queue.running?
      callback_queue << async_call
    end
def defer(callable, trans_event, *data)
      async_call = AsyncCall.new(machine, callable, trans_event, *data)
      callback_queue.start unless callback_queue.running?
      callback_queue << async_call
    end
Defer callback execution

 @api private