How to get non-homogenous options or two one-ways for a roundtrip in FlightOffersSearch API get or post call?

Question

I am using the FlightOffersSearch API and want to get 2 one-ways for a round trip search. I am also trying to get non-homogenous options in the results.

My question is what option should I send in the request to get the 2 one-ways or non-homogenous flights?

I used the FlightOffersSearch API and included the "addOneWayOffers=true" in the GET method as shown below-

https://test.api.amadeus.com/v2/shopping/flight-offers?originLocationCode=SYD&destinationLocationCode=BKK&departureDate=2023-05-01&returnDate=2023-06-01&adults=1&max=250&children=1&travelClass=PREMIUM_ECONOMY&currencyCode=USD&infants=1&addOneWayOffers=true

I am getting an error in the response as below.

{
    "errors": [
        {
            "status": 400,
            "code": 572,
            "title": "INVALID OPTION",
            "detail": "Invalid query parameter",
            "source": {
                "parameter": "addOneWayOffers"
            }
        }
    ]
}

Kindly let me know if anyone encountered this issue and was able to resolve it?