Goal:
  
  G : t
  HI : invariants
  HG : acyclic_no_loop
  x : V.t
  p : PathOf x (s G)
  H : VSet.In x (V G)
  lx : Z
  lsx : lsp (s G) x = Some lx
  w : 0 <= lx
  ============================
   (weight p <= 0)


DEBUG:Going to execute:
etransitivity
DEBUG LTAC Evaluated term: (PathOf_In ?i p)
DEBUG LTAC Evaluated term: source_vertex
DEBUG LTAC Evaluated term: (lsp_s x H)