fact: Definition Book_2_6 {A : Type} {x y z : A} (p : x = y) : IsEquiv (concat_left z p).
imports: HoTT(Basics Types HProp HSet Projective TruncType Truncations Modalities.Notnot Modalities.Open Modalities.Closed BoundedSearch Equiv.BiInv Spaces.Nat Spaces.Torus.TorusEquivCircles Metatheory.Core Metatheory.FunextVarieties)