public function addMember($entry)
{
$entry = $entry instanceof Model ? $entry->getDn() : $entry;
if (is_null($entry)) {
throw new InvalidArgumentException('Cannot add member to group. The members distinguished name cannot be null.');
}
$this->addModification(new BatchModification($this->schema->member(), LDAP_MODIFY_BATCH_ADD, [$entry]));
return $this->save();
}