proposition: Lemma dom_valid k f : k \in dom f -> 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)