proposition: Lemma contr_hfiber_cxfib' `{Univalence} {A B C : AbGroup} (E : AbSES C B) (F : AbSES (middle E) A) (p : abses_pullback (inclusion E) F $== pt) : Contr (hfiber_cxfib' E F p).
proof: Proof. srapply Build_Contr. 1: apply hfiber_cxfib'_inhabited. intros [Y q]. apply equiv_path_hfiber_cxfib'. apply hfiber_cxfib'_induced_path'. Defined.
imports: Basics Types HSet HFiber Limits.Pullback WildCat Pointed.Core Homotopy.ExactSequence Groups.QuotientGroup AbGroups.AbelianGroup AbGroups.AbPullback AbGroups.Biproduct AbSES.Core AbSES.Pullback Modalities.Identity Modalities.Modality Truncations.Core