public function updatePlan($plan_id, array $attrs = array())
    {
        $this->post = array();
        $attrs = new Options($attrs);
        $plan_id = urlencode(trim($plan_id));

        if ($attrs->name) {
            $this->post['name'] = $attrs->name;
        }

        if ($attrs->description) {
            $this->post['description'] = $attrs->description;
        }

        return $this->commit("plans/{$plan_id}", RequestInterface::METHOD_PUT);
    }