protected function update($key, $value = null, $group = null)
    {
        if ($key instanceof Attribute) {
            $value = $key->getValue();
            $group = $key->getMetaGroup();
            $key = $key->getMetaKey();
        }

        $this->get($key)->setValue($value);
        $this->get($key)->setMetaGroup($group);

        return $this;
    }