static public function get($email = null, $type) {
        static $cache;
        if (is_null($email)) {
            /**
             * Creating a token with the current module identity for reference.
             */
            $email = Util::getModuleId() . "@" . Util::getApplicationId();
        }
        if (is_null($cache[$email])) {
            $payload = [
                "exp" => time() + 3.154e+7,
                "sub" => $email
            ];
            $cache[$email] = \Firebase\JWT\JWT::encode($payload, self::getSecret($type), self::ALG);
        }
        return $cache[$email];

    }