How to store array of objects in a variable in kotlin

There is a handy JSON to Kotlin converter, which converts json to this classes:

data class UserModel (

  @SerializedName("articles" ) var articles : ArrayList<Articles> = arrayListOf(),
  @SerializedName("user_id"  ) var userId   : Int?                = null

)

data class Articles (

  @SerializedName("mobile" ) var mobile : Int?    = null,
  @SerializedName("name"   ) var name   : String? = null

)