Goal:
  
  G : t
  HI : invariants
  HG : acyclic_no_loop
  x : V.t
  y : V.t
  z : V.t
  n : Z
  Hn : lsp x y = Some n
  m : Z
  Hm : lsp y z = Some m
  p1 : SPath (V G) x y
  Hp1 : sweight p1 = n
  p2 : SPath (V G) y z
  Hp2 : sweight p2 = m
  XX : (Some (sweight (simplify2' (concat (to_pathOf p1) (to_pathOf p2)))) <=
        lsp0 (V G) x z)%nbar
  H : sweight p1 + sweight p2 <=
      sweight (simplify2' (concat (to_pathOf p1) (to_pathOf p2)))
  ============================
   (Some n + Some m <= lsp x z)%nbar


DEBUG:Going to execute:
erewrite -> Hp1, -> Hp2 in H