public function getIds()
    {
        $ids = array();
        foreach ($this->vertices as $vertex) {
            $ids []= $vertex->getId();
        }
        return $ids;
    }
public function getIds()
    {
        $ids = array();
        foreach ($this->vertices as $vertex) {
            $ids []= $vertex->getId();
        }
        return $ids;
    }
public function getIds ( ) { $ ids = array ( ) ; foreach ( $ this -> vertices as $ vertex ) { $ ids [ ] = $ vertex -> getId ( ) ; } return $ ids ; }
return array of Vertex IDs

@return array
return array of Vertex IDs