fact: Definition family_lub {P:Poset} (P_complete : is_complete P) {I:UU} (f : I -> P) : least_upper_bound f.
imports: UniMath.Foundations.All UniMath.MoreFoundations.All UniMath.Combinatorics.WellOrderedSets UniMath.OrderTheory.DCPOs.AlternativeDefinitions.Dcpo