Android - How to transform from List<T> to Observable<PageList<T>> for androidx paging library

gistfile1.kt

package com.lahaus.utils.extensions

import androidx.paging.DataSource
import androidx.paging.PagedList
import androidx.paging.PositionalDataSource
import androidx.paging.RxPagedListBuilder
import io.reactivex.Observable

fun <T> List<T>.toObservablePagedList(): Observable<PagedList<T>> {
    val defaultConfig = PagedList.Config.Builder()
        .setEnablePlaceholders(false)
        .setPageSize(size)
        .setMaxSize(size + 2)
        .setPrefetchDistance(1)
        .build()

    return RxPagedListBuilder(dataSourceFactory(this), defaultConfig)
        .buildObservable()
}

/**
 * src: https://gist.github.com/JoseAlcerreca/1e9ee05dcdd6a6a6fa1cbfc125559bba
 */
private fun <T> dataSourceFactory(itemList: List<T>): DataSource.Factory<Int, T> =
    object : DataSource.Factory<Int, T>() {
        override fun create(): DataSource<Int, T> =
            ListDataSource(itemList)
    }

/**
 * src: https://gist.github.com/JoseAlcerreca/1e9ee05dcdd6a6a6fa1cbfc125559bba
 */
private class ListDataSource<T>(private val itemList: List<T>) : PositionalDataSource<T>() {

    override fun loadRange(params: LoadRangeParams, callback: LoadRangeCallback<T>) {
        itemList.subList(params.startPosition, params.startPosition + params.loadSize)
            .toMutableList()
    }

    override fun loadInitial(params: LoadInitialParams, callback: LoadInitialCallback<T>) {
        callback.onResult(itemList, 0)
    }
}