proposition: Lemma assocsF f x : assocs (free f x) = filter (fun kv => kv.1 != x) (assocs f).
proof: Proof. by rewrite !umEX /UM.assocs; case: (UMC.from f)=>//=; case. Qed.
imports: Coq(ssreflect ssrbool ssrfun) mathcomp(ssrnat eqtype seq path bigop) pcm(options prelude finmap seqperm pred seqext) pcm(pcm morphism)