proposition: Lemma In_dom_omf f h k : k \in dom (f h) <-> exists v w, (k, w) \In h /\ map_fun f (k, w) = Some v.
proof: Proof. by case: f=>s [m H] /=; rewrite H; split=>/In_dom_omap. Qed.
imports: Coq(ssreflect ssrbool ssrfun) mathcomp(ssrnat eqtype seq path bigop) pcm(options prelude finmap seqperm pred seqext) pcm(pcm morphism)