def dequeue
      loop do
        return nil if @stop
        message = receive_message
        if message
          if message.valid?
            return message
          else
            delete_message(message)
          end
        end
      end
    end
def dequeue
      loop do
        return nil if @stop
        message = receive_message
        if message
          if message.valid?
            return message
          else
            delete_message(message)
          end
        end
      end
    end
Receive a message from SQS queue.
 @return [Barbeque::Message::Base]