proposition: Lemma can_iso : cancel iso_inv iso.
proof: Proof. Proof using B_coll L_AB. move => x. apply/B_coll => w. by rewrite delta_iso delta_iso_inv. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(fintype path fingraph finfun finset generic_quotient) RegLang(misc languages dfa)