public function setDefaultLeftAndRight() {
    $withHighestRight = $this->newNestedSetQuery()->reOrderBy($this->getRightColumnName(), 'desc')->take(1)->sharedLock()->first();

    $maxRgt = 0;
    if ( !is_null($withHighestRight) ) $maxRgt = $withHighestRight->getRight();

    $this->setAttribute($this->getLeftColumnName()  , $maxRgt + 1);
    $this->setAttribute($this->getRightColumnName() , $maxRgt + 2);
  }