ApiMapper for mapping

So regarding Real World Android. an ApiMapper interface was created.This is use to map the api to our domain model. I have a question regarding this approach.What if the api holds a list of photos for example and you want to return the list of photos.That is in petsave we get to see only one image of a pet even though the api does allow you to return multiple images. I want to know how you would do such mapping.My guess is the ApiMapper should have a condition for list. However I doubt interface can hold conditional statement.If it can please how?
Any help will be highly appreciated.