public function signedUrl($expires, array $options = [])
    {
        // May be overridden for testing.
        $signingHelper = $this->pluck('helper', $options, false)
            ?: SigningHelper::getHelper();

        $resource = sprintf(
            '/%s',
            $this->identity['bucket']
        );

        return $signingHelper->sign(
            $this->connection,
            $expires,
            $resource,
            null,
            $options
        );
    }