Section SUTT_facts.
Context {E : Type -> Type} {R1 R2 : Type} (RR : R1 -> R2 -> Prop).

Lemma sutt_inv_tau_left {E R1 R2} (RR : R1 -> R2 -> Prop) :
forall (t1: itree E R1) (t2: itree E R2),
sutt RR (Tau t1) t2 ->
sutt RR t1 t2.