public function getIndexMappedAdditionalFieldNames($defaultIfEmpty = [])
    {
        $mappingConfiguration = $this->getIndexAdditionalFieldsConfiguration();
        $mappedFieldNames = $this->getOnlyArrayKeysWhereValueIsNotAnArray($mappingConfiguration);
        return count($mappedFieldNames) == 0 ? $defaultIfEmpty : $mappedFieldNames;
    }