fact: Definition weqfrom2cellto2cellalt {XX YY: algebra_ob P} (ff gg : algebra_mor P XX YY) : algebra_2cell ff gg ≃ algebra_2cellalt ff gg.
imports: UniMath.Foundations.All UniMath.Induction.PolynomialFunctors UniMath.CategoryTheory.Core.Functors UniMath.Induction.FunctorAlgebras_legacy