proposition: Lemma domeq2_undef : dom_eq2 (undef : U1) (undef : U2).
proof: Proof. by rewrite /dom_eq2 !valid_undef !dom_undef. Qed.
imports: Coq(ssreflect ssrbool ssrfun) mathcomp(ssrnat eqtype seq path bigop) pcm(options prelude finmap seqperm pred seqext) pcm(pcm morphism)