fact: Definition free_abmonoid_unit {X : hSet} (x : X) : free_abmonoid X := presented_monoid_intro x.
imports: UniMath.MoreFoundations.Subtypes UniMath.MoreFoundations.Sets UniMath.Algebra.Monoids UniMath.Algebra.Groups UniMath.Algebra.IteratedBinaryOperations UniMath.Combinatorics.Lists