fact: Definition isAssociative_list := ∏ (x:list (list X)), iterop_list (Lists.flatten x) = iterop_list_list x.
imports: UniMath.Combinatorics.Lists UniMath.Combinatorics.FiniteSequences UniMath.Algebra.RigsAndRings UniMath.Foundations.UnivalenceAxiom UniMath.MoreFoundations.Tactics UniMath.Algebra.Groups UniMath.MoreFoundations.NegativePropositions