Goal:
  
  G1 : t
  G2 : t
  sub : full_subgraph G1 G2
  x : VSet.elt
  hx : VSet.In x (V G1)
  ============================
   (VSet.for_all (fun y : VSet.elt => lsp G1 x y == lsp G2 x y) (V G1) = true)


DEBUG:Going to execute:
<coq-core.plugins.ssreflect::ssrapply@0> $1
DEBUG LTAC Evaluated term: VSet.for_all_spec