Problem with Objective-C marshalling an "optionals" property in Nativescript

Question

I'm building a NativeScript plugin for iOS to integrate a card payment terminal as an external accessory. It is almost done, and working, but I have problem with passing one argument called "optionals". This is the whole code I'm trying to implement. It's the payworks framework for a Miura terminal. http://www.payworks.mpymnt.com/node/143

MPTransactionParameters *tp = [MPTransactionParameters chargeWithAmount:[NSDecimalNumber decimalNumberWithString:@"5.00"]
                                                               currency:MPCurrencyEUR
                                                              optionals:^(id<MPTransactionParametersOptionals>  _Nonnull optionals) {
                                                                  optionals.subject = @"Bouquet of Flowers";
                                                                  optionals.customIdentifier = @"yourReferenceForTheTransaction";
                                                              }];

I cannot find a way of sending this "optionals" function.

In the generate typing metadata I see the MPTransactionParametersOptionals is a @protocol, but still don't know how to use it here as a parameter.

This is my current javascript code for the block

const tp = MPTransactionParameters.chargeWithAmountCurrencyOptionals(
    amount,
    MPCurrencyEUR,
    function (optionals) {
        console.log(optionals); //logs the newly created MPTransactionParameters instance, with set amount and currency properties, but cannot touch or set the optional properties.
    }
  );

The 3rd parameter of chargeWithAmountCurrencyOptionals() should be a function, but I'm doing it wrong, and searched everywhere in google how to do it but no success. I'm already trying for 2 days.

It is working, when the 3rd parameter is null, but I need the set the optional properties.

EDIT: adding the metadata. There are a lot of typings for MPtransactionParameters, so I decided to give you the whole file so you can search.

https://drive.google.com/open?id=1kvDoXtGbCoeCT20b9_t2stc2Qts3VyQx

EDIT2: Adding the typings:

https://drive.google.com/open?id=1lZ3ULYHbX7DXdUQMPoZeSfyEZrjItSOS