∀ {α : Type u} {β : α → Type v} [inst : BEq α] [inst_1 : Hashable α] [EquivBEq α] [LawfulHashable α]
  {l : List ((a : α) × β a)} {k k' : α},
  (k == k') = true →
    List.Pairwise (fun a b => (a.fst == b.fst) = false) l →
      k ∈ List.map Sigma.fst l →
        ∀ {h' : (↑(Std.DHashMap.Internal.Raw₀.emptyWithCapacity.insertMany l)).contains k' = true},
          (↑(Std.DHashMap.Internal.Raw₀.emptyWithCapacity.insertMany l)).getKey k' h' = k