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kotlinlang

I have these two classes. They have identical fields with the same types, except that the second class has all of the fields mutable, nullable and initialized to null:
```
data class Dog(
        val age: Int,
        val name: String?,
        val list: List&lt;String&gt;
)
data class DogBuilder(
        var age: Int? = null,
        var name: String? = null,
        var list: List&lt;String&gt;? = null
)
```

Is there any more concise way to define these? I have a lot of fields so there is a lot of repetition.