fact: Definition map {Y} {f:ℕ->Y} (s:target_paths f) : halfline -> GuidedHomotopy f s.
imports: UniMath.Foundations.All UniMath.MoreFoundations.NullHomotopies UniMath.MoreFoundations.Nat UniMath.MoreFoundations.Notations UniMath.MoreFoundations.PartA