Goal:
  
  A : Type
  B : Type
  P : A → B → Prop
  Q : A → B → Prop
  l : list A
  l' : list B
  ============================
   (Forall2 P l l'
    → Forall (λ x : A, ∀ y : B, P x y → Q x y) l → Forall2 Q l l')


DEBUG:Going to execute:
induction 1; constructor; inversion H1