Kotlin now has support for Parcelizable objects, using the @Parcelize annotation.

Watch the next video if you want a bit of history, but don't follow along with the code changes.

Things are much easier now.  All you have to do, is add

@Parcelize

on the line before the class declaration for the Photo class.

The complete code in Photo.kt becomes:

package academy.learnprogramming.flickrbrowser    // <-- use your own package name here

import android.os.Parcelable
import kotlinx.android.parcel.Parcelize

@Parcelize
class Photo(var title: String, var author: String, var authorId: String, var link: String, var tags: String,
            var image: String) :  Parcelable

In the PhotoDetailsActivity class,  change the code to use getParcelableExtra

val photo = intent.getParcelableExtra(PHOTO_TRANSFER) as Photo

instead of getSerializableExtra.