∀ {α : Type u} [inst : BEq α] [inst_1 : Hashable α] [EquivBEq α] [LawfulHashable α] {l : List α} {k : α},
  Std.DHashMap.Raw.Const.get? (Std.DHashMap.Raw.Const.unitOfList l) k = if l.contains k = true then some () else none