proposition: Lemma validF k f : valid (free f k) = valid f.
proof: Proof. by rewrite !pcmE /= !umEX; case: (UMC.from f). Qed.
imports: Coq(ssreflect ssrbool ssrfun) mathcomp(ssrnat eqtype seq path bigop) pcm(options prelude finmap seqperm pred seqext) pcm(pcm morphism)