public function save($id, $values)
    {
        // We need to verify nonce value, before
        // we save model data to the Singularity.
        $this->nonce->verify($this->getSlug());

        // If model is preserved as single, update
        // single row with model slug as meta key.
        if ($this->isPreservedAs('single')) {
            return $this->updateMeta($id, [
                'key' => $this->getSlug(),
                'value' => $values,
            ]);
        }

        // If model is preserved as multiple, update
        // multiple rows where meta key is value key.
        if ($this->isPreservedAs('multiple')) {
            foreach ($values as $key => $value) {
                $this->updateMeta($id, [
                    'key' => $key,
                    'value' => $value,
                ]);
            }
        }
    }