public function extract(){
        foreach($this->item->getComposingElements() as $element){
            $this->extractImg($element);
            $this->extractObject($element);
            $this->extractStyleSheet($element);
            $this->extractCustomElement($element);
            if($this->getGetXinclude()){
                $this->extractXinclude($element);
            }
        }
        return $this->assets;
    }