protected function modifyGPOLinks(array $GPOs)
{
if (is_null($this->gpoLinks) && $this->getOperationType() != self::TYPE_CREATE) {
$this->gpoLinks = $this->fromLdap($this->getLastValue());
} elseif (is_null($this->gpoLinks)) {
$this->gpoLinks = [];
}
$this->validateGPOLinks($GPOs);
$this->gpoLinks = $this->modifyMultivaluedAttribute($this->gpoLinks, $GPOs);
$this->setLastValue($this->implodeGPOLinks($this->gpoLinks));
}