fun <T : Any?> problematic(lss: List<List<T>>): List<T> {
  return lss.flatMap<List<T>, @FlexibleNullability T?>(transform = local fun <anonymous>(it: List<T>): Iterable<@FlexibleNullability T?> {
    return id<@FlexibleNullability T?>(v = it) /*!! List<@FlexibleNullability T?> */
  }
)
}
