fact: Definition bounded {X : Type} (d : X -> X -> R) (A : Ensemble X) := exists x r, Included A (open_ball d x r).
imports: Topology(RationalsInReals SubspaceTopology) ZornsLemma(EnsemblesTactics DecidableDec) Coq(Reals ClassicalChoice Program.Subset) Coq(Lia Lra)