code: def may_be_null_is_nullable():
      
  
      repo = GIRepository()
      repo.require("GLib", "2.0", 0)
      info = repo.find_by_name("GLib", "spawn_sync")
      # this argument is (allow-none) and can never be (nullable)
      return not info.get_arg(8).may_be_null
docs: If may_be_null returns nullable or if NULL can be passed in.
  
      This can still be wrong if the specific typelib is older than the linked
      libgirepository.
  
      https://bugzilla.gnome.org/show_bug.cgi?id=660879#c47