GraphAware\Reco4PHP\Common\ObjectSet::valid PHP Метод

    protected function valid($element)
    {
        return $element instanceof $this->className;
    }

 /**
  * @param \GraphAware\Common\Type\NodeInterface $node
  */
 public function add(NodeInterface $node)
 {
     if (parent::valid($node) && !$this->contains($node)) {
         $this->elements[$node->identity()] = $node;
     }
 }