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

Lemma suttF_inv_tau_left {E R1 R2} (RR : R1 -> R2 -> Prop) :
forall (t1: itree E R1) ot2,
suttF RR (upaco2 (suttF RR) bot2) (TauF t1) ot2 ->
suttF RR (upaco2 (suttF RR) bot2) (observe t1) ot2.