proposition: Lemma In_omapV (h : Ur) k x : ocancel f g -> pcancel g f -> (k, x) \In (omapv f h : Ua) <-> (k, g x) \In h.
proof: Proof. move=>O P; rewrite -(In_mapv Ur _ _ _ (pcan_inj P)). by rewrite omapv_mapv // In_umfilt /= P; split=>//; case. Qed.
imports: Coq(ssreflect ssrbool ssrfun) mathcomp(ssrnat eqtype seq path bigop) pcm(options prelude finmap seqperm pred seqext) pcm(pcm morphism)