将嵌套数据类转换为Kotlin中的单层映射

基本上我有一个数据类，比如

data class House(
  val bedroom: Bedroom,
  val livingroom: Livingroom
)

data class Bedroom(
  val bed: String,
  val pillows: List<String>
)

data class Livingroom(
  val sofa: String,
  val tv: String
)

我尝试使用gson，首先将其转换为json，然后转换为map，但它会给我嵌套的map

{
   bed = "some-bed",
   pillows = ["pillow-a", "pillow-b", "pillow-c"],
   sofa = "some-sofa",
   tv = "some-tv"
}