/**
  * @return MessageHandler\MessageHandlerId
  */
 public function messageHandlerId()
 {
     if (is_null($this->messageHandlerId)) {
         $this->messageHandlerId = MessageHandler\MessageHandlerId::fromString($this->payload['message_handler_id']);
     }
     return $this->messageHandlerId;
 }
 /**
  * @return MessageHandlerId
  */
 public function messageHandlerId()
 {
     if (is_null($this->messageHandlerId)) {
         $this->messageHandlerId = MessageHandlerId::fromString($this->aggregateId());
     }
     return $this->messageHandlerId;
 }
 /**
  * @return MessageHandlerId
  */
 public function nextMessageHandlerId()
 {
     return MessageHandlerId::fromString($this->payload['next_message_handler_id']);
 }
 /**
  * @return MessageHandlerId
  */
 public function firstMessageHandlerId()
 {
     return MessageHandlerId::fromString($this->payload['first_message_handler']);
 }