public function containsOne($field, $model)
    {
        if (is_array($field) && $field[0]) {
            $field['name'] = $field[0];
            unset($field[0]);
        }
        if ($e = $this->hasElement(is_string($field) ? $field : $field['name'])) {
            $e->destroy();
        }
        $this->add('Relation_ContainsOne', $field)
            ->setModel($model);
    }