∀ {α : Type u} {β : Type v} [inst : BEq α] [EquivBEq α] {l₁ : List ((_ : α) × β)} {l₂ : List α} {k : α},
  Std.Internal.List.DistinctKeys l₁ →
    l₂.contains k = false →
      Std.Internal.List.getValue? k (List.filter (fun p => !l₂.contains p.fst) l₁) = Std.Internal.List.getValue? k l₁