∀ {α : Type u} [inst : BEq α] [inst_1 : Hashable α] {β : Type v} [EquivBEq α] [LawfulHashable α] {l : List (α × β)}
  {k fallback : α},
  (List.map Prod.fst l).contains k = false → (Std.DHashMap.Raw.Const.ofList l).getKeyD k fallback = fallback