Simple::receive

public function receive(): ?InterfacesMessage
{
	$handledMessageMap = $this->getHandledMessageMap();

	/** @var HandledMessage $row */
	if ($row = $handledMessageMap->fetch())
	{
		$message = $row->getMessage();
		$message->setHeader(self::HANDLED_MESSAGE_HEADER_NAME, $row->getId());
	}

	return null;
}