fact: Definition chain_lub' {P : Poset} (P_CC : is_chain_complete P) {I:UU} (p:I->P) : is_chain p -> least_upper_bound p.
imports: UniMath.Foundations.All UniMath.MoreFoundations.All UniMath.Combinatorics.WellOrderedSets UniMath.OrderTheory.DCPOs.AlternativeDefinitions.Dcpo