Retrieve the base plan bought from queryPurchasesAsync Billing Library V8

I am using Kotlin Google Play Billing Library 8 to query the subscriptions already bought by the user. I can get purchaseToken and subscription ProductId BUT unfortunately there is no information about the base plan (or offer) that is bought by the user. How can I retreive the base plan related to a purchaseToken. I want to do it locally via Billing Library not by sending purchase token to my server and ask from the Google.

suspend fun queryCurrentPurchases(){           
        val purchaseResult = billingClient.queryPurchasesAsync(
            QueryPurchasesParams.newBuilder().setProductType(ProductType.SUBS).build())
        if (purchaseResult.billingResult.responseCode==BillingResponseCode.OK){
            purchaseResult.purchasesList.forEach {
                println("${it.purchaseToken}, ${it.isAcknowledged}")
                it.products.forEach { productId -> println(productId)}
                //I need to know what base plan user has bought
            }
        }
}