proposition: Lemma Transitive_optionR : Transitive R -> Transitive optionR.
proof: Proof. by move=>t; case=>[x|]; case=>[y|]; case=>[z|] //=; apply: t. Qed.
imports: Coq(ssreflect ssrbool ssrfun Setoid) mathcomp(ssrnat seq eqtype) pcm(options)