fact: Definition tau {X Y : UU} {f g : X → Y} (x : A) (u : B x → X) (v : ∏ (y : B x), f (u y) = g (u y)) : x,, u ;; f = tpair (λ a : A, B a → Y) x (u ;; g).
imports: UniMath.Foundations.All UniMath.Induction.PolynomialFunctors UniMath.CategoryTheory.Core.Functors UniMath.Induction.FunctorAlgebras_legacy