mapToTranslationCode example

$codedTranslations = [];

        $referenceDefinition = $associationField->getReferenceDefinition();
        $entitySerializer = $this->serializerRegistry->getEntity($referenceDefinition->getEntityName());

        /** @var TranslationEntity $translation */
        foreach ($translations as $languageId => $translation) {
            if ($translation instanceof TranslationEntity) {
                $languageId = $translation->getLanguageId();
            }

            $translationCode = $this->mapToTranslationCode($languageId);
            $result = iterator_to_array($entitySerializer->serialize($config, $referenceDefinition, $translation));

            $codedTranslations[$translationCode] = $result;
            if ($languageId === Defaults::LANGUAGE_SYSTEM) {
                $codedTranslations['DEFAULT'] = $codedTranslations[$translationCode];
            }
        }

        yield $associationField->getPropertyName() => $codedTranslations;
    }