proposition: Lemma valid_sel (T : finType) (Us : T -> pcm) tag (x : FinProd Us) : valid x -> valid (sel tag x).
proof: Proof. by move/forallP; apply. Qed.
imports: Coq(ssreflect ssrbool ssrfun) mathcomp(ssrnat eqtype seq bigop fintype finset) pcm(options axioms prelude seqperm pred seqext)