public function getGrant(string $grantType): GrantInterface
    {
        if ($this->hasGrant($grantType)) {
            return $this->grants[$grantType];
        }

        // If we reach here... then no grant was found. Not good!
        throw OAuth2Exception::unsupportedGrantType(sprintf(
            'Grant type "%s" is not supported by this server',
            $grantType
        ));
    }