How to use the jsrsasign.KJUR.crypto function in jsrsasign

.then(data => {
     var pk = KEYUTIL.getKey(data);
     var sig = new KJUR.crypto.Signature({"alg": "SHA512withRSA"}); // Use "SHA1withRSA" for QZ Tray 2.0 and older
     sig.init(pk);
     sig.updateString(hash);
     var hex = sig.sign();
     console.log("DEBUG: \n\n" + stob64(hextorstr(hex)));
     resolve(stob64(hextorstr(hex)));
   })
   .catch(err => console.error(err));

constructor(pem) {
        const method = 'constructor';
        LOG.entry(method, pem);
        this.pem = pem;
        this.certificate = new X509();
        this.certificate.readCertPEM(pem);
        this.publicKey = KEYUTIL.getPEM(this.certificate.getPublicKey());
        this.identifier = KJUR.crypto.Util.hashHex(this.certificate.getPublicKey().pubKeyHex, 'sha256');
        this.issuer = KJUR.crypto.Util.hashHex(this.certificate.getIssuerString(), 'sha256');
        this.name = /(\/CN=)(.*?)(\/|,|$)/.exec(this.certificate.getSubjectString())[2];
        LOG.exit(method);
    }

constructor(pem) {
        const method = 'constructor';
        LOG.entry(method, pem);
        this.pem = pem;
        this.certificate = new X509();
        this.certificate.readCertPEM(pem);
        this.publicKey = KEYUTIL.getPEM(this.certificate.getPublicKey());
        this.identifier = KJUR.crypto.Util.hashHex(this.certificate.getPublicKey().pubKeyHex, 'sha256');
        this.issuer = KJUR.crypto.Util.hashHex(this.certificate.getIssuerString(), 'sha256');
        this.name = /(\/CN=)(.*?)(\/|,|$)/.exec(this.certificate.getSubjectString())[2];
        LOG.exit(method);
    }

private generate_at_hash(access_token: any): string {
        const hash = KJUR.crypto.Util.hashString(access_token, 'sha256');
        const first128bits = hash.substr(0, hash.length / 2);
        const testdata = hextob64u(first128bits);

        return testdata;
    }
}

private generate_at_hash(access_token: any): string {
        const hash = KJUR.crypto.Util.hashString(access_token, 'sha256');
        const first128bits = hash.substr(0, hash.length / 2);
        const testdata = hextob64u(first128bits);

        return testdata;
    }

encryptValue(value) : string {
    var keyObj = KEYUTIL.getKey(this.key);//this.session.keys[0]);//sessionObj.keys[0]);
    var hex = KJUR.crypto.Cipher.encrypt(value, keyObj);

    return '{enc}' + hextob64(hex);
  }

generate_code_verifier(code_challenge: any): string {
        const hash = KJUR.crypto.Util.hashString(code_challenge, 'sha256');
        const testdata = hextob64u(hash);

        return testdata;
    }
}

private generate_at_hash(access_token: any): string {
        const hash = KJUR.crypto.Util.hashString(access_token, 'sha256');
        const first128bits = hash.substr(0, hash.length / 2);
        const testdata = hextob64u(first128bits);

        return testdata;
    }