proposition: Lemma lastkey_omfE h : last_key h \in dom (f h) -> last_key (f h) = last_key h.
proof: Proof. by apply: lastkey_subdom omf_subdom. Qed.
imports: Coq(ssreflect ssrbool ssrfun) mathcomp(ssrnat eqtype seq path interval) pcm(options prelude pred finmap rtc seqext useqord uslice uconsec)