∀ {α : Type u} [inst : BEq α] [EquivBEq α] {β : Type v} {γ : Type w} {f : α → β → γ} {l : List ((_ : α) × β)} {k : α},
  Std.Internal.List.DistinctKeys l →
    ∀ {h : Std.Internal.List.containsKey k (List.map (fun p => ⟨p.fst, f p.fst p.snd⟩) l) = true},
      Std.Internal.List.getValue k (List.map (fun p => ⟨p.fst, f p.fst p.snd⟩) l) h =
        f (Std.Internal.List.getKey k l ⋯) (Std.Internal.List.getValue k l ⋯)