∀ {α : Type u} {β : Type v} [inst : BEq α] [inst_1 : Hashable α] {m : Std.HashMap.Raw α β} [inst_2 : EquivBEq α]
  [LawfulHashable α] {k k' : α} {f : β → β},
  m.WF → (m.modify k f).getKey? k' = if (k == k') = true then if k ∈ m then some k else none else m.getKey? k'