how to print method variables using frida

Question

this is my method i want to print the value of session id and device id , this is my code also suggest some documentation where i can learn more about frida

  public static String generateHashForDeviceSignature() {
    String sessionId = AppUtil.getSessionId();
    if (AppUtil.getDeviceId() == null || AppUtil.getDeviceId().equals("")) {
        AppUtil.setUniqueDeviceID(AppUtil.getAppContext());
    }
    String deviceId = AppUtil.getDeviceId();
    new SecureRandom().nextBytes(new byte[1024]);
    StringBuilder sb = new StringBuilder();
    if (!TextUtils.isEmpty(sessionId)) {  deviceId = sessionId + "|" + deviceId;
        }
        try {
            MessageDigest instance = MessageDigest.getInstance("SHA-256");
            instance.update(deviceId.getBytes());
            byte[] digest = instance.digest();
            int length = digest.length;
            for (int i = 0; i < length; i++) {
                sb.append(String.format("%02x", new Object[]{Integer.valueOf(digest[i] &255)}));             
            }
        } catch (Exception unused) {
        }
        return sb.toString();
        }
     }

this is my method i want to print the value of session id and device id , this is my code also suggest some documentation where i can learn more about frida.

    Java.perform(() => {
    var classInstanceIdResult = Java.use('com.androidapp.main.utils.CryptoUtil');
    var classInstanceIdAppUtil = Java.use('com.androidapp.main.utils.AppUtil');
    var getTokenMethod = classInstanceIdResult.generateHashForDeviceSignature.overload();
    var getgetDeviceId = classInstanceIdResult.getDeviceId.overload();
    var getgetSessionId = classInstanceIdResult.getSessionId.overload();
    // replace the getToken() method with out own implementation
    getTokenMethod.implementation = function () {
    // call the orignal method
     var ret = getTokenMethod.call(this);
    // do something with ret
    console.log("deviceId: " + ret.deviceId);
    console.log("Token: " + ret);
    return ret;
    };

I can print the final out put of the method but saying undefined on variable console log.