∀ {α : Type u} {β : α → Type v} [inst : BEq α] [inst_1 : Hashable α] [inst_2 : LawfulBEq α] {l : List ((a : α) × β a)}
  {k : α},
  (List.map Sigma.fst l).contains k = false →
    (↑(Std.DHashMap.Internal.Raw₀.emptyWithCapacity.insertMany l)).get? k = none