fact: Definition chain_op {C : category} (ch : chain C) : cochain (opp_cat C).
imports: UniMath.Foundations.All UniMath.CategoryTheory.Core.Categories UniMath.CategoryTheory.Core.Functors UniMath.CategoryTheory.OppositeCategory.Core UniMath.CategoryTheory.Limits.Cones UniMath.CategoryTheory.Limits.Graphs.Colimits UniMath.CategoryTheory.Limits.Graphs.Limits UniMath.CategoryTheory.Chains.Chains UniMath.CategoryTheory.Chains.Cochains