fact: Definition abses_pullback {A B B' : AbGroup} (f : B' $-> B) : AbSES B A -> AbSES B' A.
imports: Basics Types HSet Limits.Pullback WildCat Pointed.Core Homotopy.ExactSequence Modalities.ReflectiveSubuniverse AbGroups.AbelianGroup AbGroups.AbPullback AbGroups.Biproduct AbSES.Core AbSES.DirectSum