proposition: Lemma dom_omfUn f h1 h2 : dom (f (h1 \+ h2)) =i [pred x | valid (h1 \+ h2) & (x \in dom (f h1)) || (x \in dom (f h2))].
proof: Proof. by case: f=>s [m H] /= x; rewrite !H dom_omapUn. Qed.
imports: Coq(ssreflect ssrbool ssrfun) mathcomp(ssrnat eqtype seq path bigop) pcm(options prelude finmap seqperm pred seqext) pcm(pcm morphism)