proposition: Lemma size_assocs f : size (assocs f) = size (dom f).
proof: Proof. by rewrite assocs_dom size_map. Qed.
imports: Coq(ssreflect ssrbool ssrfun) mathcomp(ssrnat eqtype seq path bigop) pcm(options prelude finmap seqperm pred seqext) pcm(pcm morphism)