public function add_child($element)
{
if (!$element instanceof backup_optigroup_element) {
// parameter must be backup_optigroup_element
if (is_object($element)) {
$found = get_class($element);
} else {
$found = 'non object';
}
throw new base_optigroup_exception('optigroup_element_incorrect', $found);
}
parent::add_child($element);
}
public function is_multiple()
{
return parent::is_multiple();
}