fact: Definition free_abmonoid_hrel (X : hSet) : hrel (free_monoid X) := λ g h, ∃ x y, x * y = g × y * x = h.
imports: UniMath.MoreFoundations.Subtypes UniMath.MoreFoundations.Sets UniMath.Algebra.Monoids UniMath.Algebra.Groups UniMath.Algebra.IteratedBinaryOperations UniMath.Combinatorics.Lists