public function cObjGetSingleExt(
        /** @noinspection PhpUnusedParameterInspection */ $name,
        array $configuration,
        /** @noinspection PhpUnusedParameterInspection */ $TyposcriptKey,
        $parentContentObject
    ) {
        $this->configuration = array_merge($this->configuration, $configuration);

        $relatedItems = $this->getRelatedItems($parentContentObject);

        if (!empty($this->configuration['removeDuplicateValues'])) {
            $relatedItems = array_unique($relatedItems);
        }

        if (empty($configuration['multiValue'])) {
            // single value, need to concatenate related items
            $singleValueGlue = !empty($configuration['singleValueGlue']) ? trim($configuration['singleValueGlue'], '|') : ', ';
            $result = implode($singleValueGlue, $relatedItems);
        } else {
            // multi value, need to serialize as content objects must return strings
            $result = serialize($relatedItems);
        }

        return $result;
    }