Transformation error after Kotlin Migration

Question

I haven't touched this source code for half a year. Recently, before I touched anything, I decided to update the following: AGP, Gradle, dependencies and Kotlin Migration.

Code:

Placeholder Fragment

class myPlaceholderFragment : Fragment() {

    private lateinit var myPageViewModel: MyPageViewModel

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        myPageViewModel = ViewModelProvider(this).get(MyPageViewModel::class.java).apply {
            setIndex(arguments?.getInt(ARG_SECTION_NUMBER) ?: 1)
        }

    }

    override fun onCreateView(
        inflater: LayoutInflater, container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {
        val root = inflater.inflate(R.layout.fragment_my_main, container, false)
        val textView: TextView = root.findViewById(R.id.my_main_section_label)
        myPageViewModel.text.observe(viewLifecycleOwner, {
            textView.text = it
        })
        return root
    }
}

PageViewModel

class myPageViewModel : ViewModel() {

    private val _index = MutableLiveData<Int>()
        val text: LiveData<String> = Transformations.map(_index) {
           "Hello world from section: $it"
       }

    fun setIndex(index: Int) {
        _index.value = index
    }
}

Error:

Unresolved reference: Transformations