fact: Definition is_chain_in_subposet {P : Poset} {A : Subposet P} {I : Type} (p : I -> A) : is_chain p <-> is_chain (subposet_incl ∘ p).
imports: UniMath.Foundations.All UniMath.MoreFoundations.All UniMath.Combinatorics.WellOrderedSets UniMath.OrderTheory.DCPOs.AlternativeDefinitions.Dcpo