And Dev Affirmations; unresolved reference ItemAdapter

Question

This is verbatum from the affirmations.kt in android developer training. In class MainActivity, the ItemAdapter in "recyclerView.adapter = ItemAdapter(this, myDataset)" line has an error, unresolved reference, ItemAdapter. also, the import com.example.affirmations.adapter.ItemAdapter produces an unresolved reference on adapter.

Any help? Edited: corrected incorrect variable name from myDatatest to myDataset

package com.example.affirmations.adapter

import android.content.Context
import android.view.LayoutInflater
import android.view.View
import android.view.ViewGroup
import android.widget.TextView
import androidx.recyclerview.widget.RecyclerView
import com.example.affirmations.R
import com.example.affirmations.model.Affirmation

/**
 * Adapter for the [RecyclerView] in [MainActivity]. Displays [Affirmation]data object
 */
class ItemAdapter(
    private val context: Context,
    private val dataset: List<Affirmation>
) : RecyclerView.Adapter<ItemAdapter.ItemViewHolder>() {

    //Provide a reference to the views for each data item
    //Complex data items may need more than one view per item, and
    //you provide access to all the views for a data item in a view holder.
    //Each data item is just an Affirmation object.
    class ItemViewHolder(private val view: View) : RecyclerView.ViewHolder(view){
        val textView: TextView = view.findViewById(R.id.item_title)

    }

    /**
     * Create new views (invoked by the layout manager)
     */
    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ItemViewHolder {
        //create a new view
        val adapterLayout = LayoutInflater.from(parent.context)
            .inflate(R.layout.list_item, parent, false)

        return ItemViewHolder(adapterLayout)
    }

    /**
     * Replace the contents of a view (invoked by the layout manager)
     */

    override fun onBindViewHolder(holder: ItemViewHolder, position: Int) {
        val item =dataset[position]
        holder.textView.text = context.resources.getString((item.stringResourceId))

    }
    /**
     * Return the size of your dataset (invoked by the layout manager.)
     */

    override fun getItemCount()= dataset.size
}

package com.example.affirmations

import com.example.affirmations.data.Datasource
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import androidx.recyclerview.widget.RecyclerView
import com.example.affirmations.adapter.ItemAdapter


class MainActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        //Initialize data.
        val myDataset = Datasource().loadAffirmations()

        val recyclerView = findViewById<RecyclerView>(R.id.recycler_view)
        recyclerView.adapter = ItemAdapter(this, myDataset)


        //Use this setting to imporove performance if you know that changes
        //in content do not change the layout size of the RecyclerView
        recyclerView.setHasFixedSize(true)
    }
}