Cloud Functions in Firebase: call parameter to be type Document Snapshot

I am trying to use cloud functions to get a subcollection from a starting point. My cloud function is written in typescript and goes by:

export async function getCollection(path: any, start:any, orderBy: any) {
    return  admin
    .firestore()
    .collection(path)
    .orderBy(orderBy)
    .startAfter(start)
    .limit(10)
    .get()
    .then(snapshot => snapshot.docs.map(doc => ({ id: doc.id, ...doc.data() })));
}

My code in Kotlin to call for the cloud function from my android app is:

fun getReleasedAnimalsData(startAfter: DocumentSnapshot):Task<ReleasedData>{
    /*val gsonObject = Gson().toJson(startAfter)
    val jsonObject = JSONObject(gsonObject)*/
    val data = hashMapOf("startAt" to startAfter)
    return functions
        .getHttpsCallable("function")
        .call(data)
        .continueWith { task ->
            val json = Gson().toJson(task.result?.data)
            val returnedData= Gson().fromJson(json,ReleasedData::class.java)
            returnedData
        }
}

When I try to do the calling, I get the following error:

Object cannot be encoded in JSON: DocumentSnapshot

I understand that Document Snapshot is a complex object and cant be serialized just like that but I cant seem to find the way to call the startAfter property from Firebase without a document snapshot.

You might be wondering: Why is he not making the call from the Android Firebase SDK? That is because this task I am trying to do is part of a bigger algorithm and I would prefer to only do one call to the instead of many calls from the android app. Is there a way to make this possible? Or should I just give up and use my Coroutines to do more than one async call?

Any help is appreciated! :)