Goal:
  
  G : t
  HG : acyclic_no_loop
  x : V.t
  y : V.t
  z : V.t
  e : EdgeOf x y
  p : PathOf y z
  IHp : weight p <= sweight (simplify2 p)
  F0 : false = true -> VSet.In x (snodes (simplify2 p))
  F1 : ~ VSet.In x (snodes (simplify2 p)) <-> false = false
  ============================
   (e.π1 + weight p <= e.π1 + sweight (simplify2 p))


DEBUG:Going to execute:
match goal with
           | |- ?X1 -> ?X2 => intro
           | |- ~ _ => unfold not at 1; intro
           end