fact: Definition abses_pullback_projection `{Univalence} {B A : AbGroup} (E : AbSES B A) : pt = abses_pullback (projection E) E := abses_pullback_component1_id (abses_pullback_projection_morphism E) (fun _ => idpath).
imports: Basics Types HSet Limits.Pullback WildCat Pointed.Core Homotopy.ExactSequence Modalities.ReflectiveSubuniverse AbGroups.AbelianGroup AbGroups.AbPullback AbGroups.Biproduct AbSES.Core AbSES.DirectSum