Goal:
    G : t  s0 : VSet.t  x : V.t
  ============================
   (forall (z : V.t) (e : EdgeOf x z) (s' : VSet.t)
      (Hs : DisjointAdd x s0 s'),
    sweight (add_end (spath_refl s0 x) e Hs) =
    sweight (spath_refl s0 x) + e.π1)


DEBUG:Going to execute:
intros