Goal:
    G1 : t  ext : EdgeSet.t  v : VSet.elt  s : VSet.t  H1 : VSet.In v (V G1)
  ============================
   (~ VSet.In v (V G1) -> False)


DEBUG:Going to execute:
by apply
DEBUG LTAC Evaluated term: E
DEBUG LTAC Evaluated term: VSetFact.not_mem_iff
DEBUG LTAC Evaluated term: (iffRL (P:=~ VSet.In v (V G1))
                              (VSetFact.not_mem_iff (V G1) v) _view_subject_)