∀ {α : Type u} {x : BEq α} {x_1 : Hashable α} {β : Type v} {m : Std.ExtDHashMap α fun x => β} [inst : EquivBEq α]
  [inst_1 : LawfulHashable α] {l : List (α × β)} {k k' : α},
  (k == k') = true →
    List.Pairwise (fun a b => (a.1 == b.1) = false) l →
      k ∈ List.map Prod.fst l →
        ∀ {h : k' ∈ Std.ExtDHashMap.Const.insertMany m l}, (Std.ExtDHashMap.Const.insertMany m l).getKey k' h = k