code: def get_exclusions(self):
          
          all_packages = (
              pkg
              for ns_pkg in self._get_SVEM_NSPs()
              for pkg in self._all_packages(ns_pkg)
          )
  
          excl_specs = product(all_packages, self._gen_exclusion_paths())
          return set(starmap(self._exclude_pkg_path, excl_specs))
docs: Return a collections.Sized collections.Container of paths to be
          excluded for single_version_externally_managed installations.