public function getField($fieldDefIdentifier, $languageCode = null)
    {
        if (null === $languageCode) {
            $languageCode = $this->versionInfo->contentInfo->mainLanguageCode;
        }

        if (isset($this->fields[$fieldDefIdentifier][$languageCode])) {
            return $this->fields[$fieldDefIdentifier][$languageCode];
        }

        return null;
    }