Goal:
    G1 : t  G2 : t  hsub : full_subgraph G1 G2
  ============================
   (is_true
      (VSet.for_all
         (fun x : VSet.elt =>
          VSet.for_all (fun y : VSet.elt => lsp G1 x y == lsp G2 x y)
            (border_set G1 (EdgeSet.diff (E G2) (E G1))))
         (border_set G1 (EdgeSet.diff (E G2) (E G1)))))


DEBUG:Going to execute:
<coq-core.plugins.ssreflect::ssrset@0> $1 $2 $3