class CatFragment: Fragment() {
    companion object {
        fun newInstance(catId: String) = CatFragment().withArgs {
             putString("catId", catId)
        }
    }
}
class DogFragment: Fragment() {
    companion object {
        fun newInstance(dogId: String) = DogFragment().withArgs {
             putString("dogId", dogId)
        }
    }
}

inline fun <T: Fragment> T.withArgs(
                             argsBuilder: Bundle.() -> Unit): T =
    this.apply {
        arguments = Bundle().apply(argsBuilder)
    }

// if(something != null && something.thingy) {
//     ...
// } else {
//     ...
// }

something?.takeIf { it.thingy }?.let {
   ...
} ?: {
   ...
}