Goal:
  
  G : t
  HI : invariants G
  HG : acyclic_no_loop G
  n : Z
  x : V.t
  y : V.t
  n0 : (Some n <= lsp G x y)%nbar -> False
  ============================
   ((Some n <= lsp G x y)%nbar <-> false)


DEBUG:Going to execute:
fun tauto_flags X1 X2 id =>
             <coq-core.plugins.tauto::flatten_contravariant_disj@0>