src/Models/ResponseItemData.php
public function callbackCustomData($value, $raw) {
        $defaultKeys = ['id','slugs','data','type','href','tags','lang','alternate_languages','linked_documents','first_publication_date','last_publication_date'];
        foreach($raw as $key => $value) {
            if(in_array($key, $defaultKeys)) {
                unset($raw[$key]);
            }
        }
        return $raw;
    }
public function callbackCustomData($value, $raw) {
        $defaultKeys = ['id','slugs','data','type','href','tags','lang','alternate_languages','linked_documents','first_publication_date','last_publication_date'];
        foreach($raw as $key => $value) {
            if(in_array($key, $defaultKeys)) {
                unset($raw[$key]);
            }
        }
        return $raw;
    }
Return all the values that are not default in Prismic

@param $value
@param $raw
@return mixed