proposition: Lemma In_omap a k v w f : (k, w) \In f -> a (k, w) = Some v -> (k, v) \In omap a f.
proof: Proof. by move=>H1 H2; apply/In_omapX=>//; exists w. Qed.
imports: Coq(ssreflect ssrbool ssrfun) mathcomp(ssrnat eqtype seq path bigop) pcm(options prelude finmap seqperm pred seqext) pcm(pcm morphism)