proposition: Lemma uniq_app_1 : uniq (E ++ F) -> uniq E.
proof: Proof. clear. intros J. alist induction E. apply uniq_nil. inversion J; subst. rewrite dom_app in *. apply uniq_push. auto. fsetdec. Qed.
imports: Coq.FSets.FSets Coq.Lists.List Coq.Logic.Decidable Coq.Strings.String String Metalib.CoqFSetDecide Metalib.CoqListFacts Metalib.LibTactics Metalib.CoqFSetInterface Coq.Classes.Equivalence Coq.Classes.EquivDec Metalib.CoqEqDec