Goal:
  
  A : Type
  P : list A → list A → A → A → Type
  Γ : list A
  H : All2_fold P Γ Γ
  ============================
   (All_fold (λ (Γ : list A) (d : A), P Γ Γ d d) Γ)


DEBUG:Going to execute:
match goal with
           | H':_ |- _ => match H' with
                          | H => idtac
                          end
           end