How to use the jose.JWS function in jose

if (!alg) {
    const algs = new Set();

    keystore.all().forEach((key) => {
      key.algorithms('sign').forEach(Set.prototype.add.bind(algs));
    });

    const supported = this.issuer[`${endpoint}_endpoint_auth_signing_alg_values_supported`];
    alg = Array.isArray(supported) && supported.find((signAlg) => algs.has(signAlg));
  }

  const key = keystore.get({ alg, use: 'sig' });
  if (!key) {
    throw new TypeError(`no key found in client jwks to sign a client assertion with using alg ${alg}`);
  }
  return jose.JWS.sign(payload, key, { alg, typ: 'JWT', kid: key.kid });
}

const symmetric = alg.startsWith('HS');
      if (symmetric) {
        key = await this.joseSecret();
      } else {
        const keystore = instance(this).get('keystore');

        if (!keystore) {
          throw new TypeError(`no keystore present for client, cannot sign using alg ${alg}`);
        }
        key = keystore.get({ alg, use: 'sig' });
        if (!key) {
          throw new TypeError(`no key to sign with found for alg ${alg}`);
        }
      }

      signed = jose.JWS.sign(payload, key, {
        ...header,
        kid: symmetric ? undefined : key.kid,
      });
    }

    if (!algorithms.encrypt.alg) {
      return signed;
    }

    const fields = { alg: algorithms.encrypt.alg, enc: algorithms.encrypt.enc, cty: 'JWT' };

    if (fields.alg.match(/^(RSA|ECDH)/)) {
      key = await this.issuer.key({
        alg: fields.alg,
        enc: fields.enc,
        use: 'enc',