proposition: Lemma transDleU: transD <3= transU.
proof: Proof. intros. destruct PR. econstructor; eauto using eqit_mon. Qed.
imports: Coq(Setoid Morphisms Relations) Paco(paco) ITree(Basics.Utils Core.ITreeDefinition Eq.Eqit Eq.Paco2 Eq.Shallow)