fact: Hypothesis P_associativity : forall x1 x2 x3 x4 (m1 : mor x1 x2) (m2 : mor x2 x3) (m3 : mor x3 x4), compose (compose m3 m2) m1 = compose m3 (compose m2 m1).
imports: HoTT.Tactics Types.Forall Types.Sigma Basics.Trunc Category.Core Functor.Core Category.Sigma.Core Functor.Paths