Goal:
  
  G1 : t
  G2 : t
  __view_subject_4_ : VSet.Subset (V G1) (V G2)
  __view_subject_5_ : EdgeSet.Subset (E G1) (E G2)
  __view_subject_6_ : s G1 = s G2
  h : VSet.For_all
        (fun x : VSet.elt =>
         VSet.for_all (fun y : VSet.elt => lsp G1 x y == lsp G2 x y) (V G1) =
         true) (V G1)
  ============================
   (subgraph G1 G2)


DEBUG:Going to execute:
<coq-core.plugins.ltac::discriminate@0>
Level 0: Backtrace:

Cannot apply lemma eq_sym
Level 0: Backtrace:

Cannot apply lemma eq_sym
Level 0: Backtrace:

Cannot apply lemma eq_sym