proposition: Theorem is_functor_fam_to_slice : is_functor fam_to_slice_data.
proof: Proof. split; [intro f | intros f f' f'' F F']; apply eq_mor_slicecat. + apply funextsec. intro p. reflexivity. + reflexivity. Qed.
imports: UniMath.Foundations.Sets UniMath.CategoryTheory.Core.Isos UniMath.CategoryTheory.Core.NaturalTransformations UniMath.CategoryTheory.Core.Categories UniMath.CategoryTheory.Core.Functors UniMath.CategoryTheory.Categories.HSET.Core UniMath.CategoryTheory.Categories.HSET.MonoEpiIso UniMath.CategoryTheory.Categories.HSET.Univalence UniMath.CategoryTheory.Categories.HSET.Slice UniMath.CategoryTheory.slicecat UniMath.CategoryTheory.Adjunctions.Core UniMath.CategoryTheory.Equivalences.Core UniMath.CategoryTheory.FunctorCategory UniMath.CategoryTheory.Groupoids UniMath.CategoryTheory.Categories.StandardCategories