proposition: Lemma In_range_valid k f : k \In range f -> valid f.
proof: Proof. by case/In_rangeX=>v /In_dom/dom_valid. Qed.
imports: Coq(ssreflect ssrbool ssrfun) mathcomp(ssrnat eqtype seq path bigop) pcm(options prelude finmap seqperm pred seqext) pcm(pcm morphism)