∀ {α : Type u} {x : BEq α} {x_1 : Hashable α} {β : α → Type v} {m : Std.ExtDHashMap α β} [inst : EquivBEq α]
  [inst_1 : LawfulHashable α] [inst_2 : Inhabited α] {k a : α} {v : β k},
  (m.insert k v).getKey! a = if (k == a) = true then k else m.getKey! a