fact: Axiom uniq_insert_mid : uniq (G ++ E) -> ~ In x (dom G) -> ~ In x (dom E) -> uniq (G ++ (x ~ a) ++ E).
imports: Coq.FSets.FSets Coq.Lists.List Coq.Logic.Decidable Metalib.CoqFSetDecide Metalib.CoqListFacts Metalib.AssocList Metalib.MetatheoryAtom Metalib.LibTactics