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