∀ {α : Type u} {β : α → Type v} {m : Std.DHashMap.Raw α β} [inst : BEq α] [inst_1 : Hashable α] [EquivBEq α]
  [LawfulHashable α] [inst_4 : Inhabited α], m.WF → ∀ {a : α}, m.getKey! a = m.getKeyD a default