public function activity($account, $repo, $id = 0)
    {
        $endpoint = sprintf('repositories/%s/%s/pullrequests/', $account, $repo);

        if ($id === 0) {
            $endpoint .= 'activity';
        } else {
            $endpoint .= $id.'/activity';
        }

        return $this->getClient()->setApiVersion('2.0')->get($endpoint);
    }