fact: Definition ac_set {G:gr} (X:Action G) := pr1 X.
imports: UniMath.Foundations.All UniMath.MoreFoundations.Propositions UniMath.MoreFoundations.Notations UniMath.MoreFoundations.Univalence UniMath.MoreFoundations.Tactics UniMath.Algebra.Monoids UniMath.Algebra.Groups UniMath.Combinatorics.OrderedSets