∀ {α : Type u} {β : Type v} {m : Std.HashMap.Raw α β} [inst : BEq α] [inst_1 : Hashable α] [EquivBEq α]
  [LawfulHashable α], m.WF → ∀ {k : α}, (List.find? (fun x => x.1 == k) m.toList = none) = (k ∉ m)