Goal:
    G1 : t  G2 : t
  ============================
   (VSet.subset (V G1) (V G2) && EdgeSet.subset (E G1) (E G2) &&
    (s G1 == s G2) &&
    VSet.for_all
      (fun x : VSet.elt =>
       VSet.for_all (fun y : VSet.elt => lsp G1 x y == lsp G2 x y) (V G1))
      (V G1) <-> full_subgraph G1 G2)


DEBUG:Going to execute:
fun => <coq-core.plugins.ltac::split@0>