fact: Axiom uniq_cons_iff : uniq ((x, a) :: E) <-> uniq E /\ ~ In x (dom E).
imports: Coq.FSets.FSets Coq.Lists.List Coq.Logic.Decidable Metalib.CoqFSetDecide Metalib.CoqListFacts Metalib.AssocList Metalib.MetatheoryAtom Metalib.LibTactics