code: def _get_SVEM_NSPs(self):
          
          # TODO: is it necessary to short-circuit here? i.e. what's the cost
          # if get_finalized_command is called even when namespace_packages is
          # False?
          if not self.distribution.namespace_packages:
              return []
  
          install_cmd = self.get_finalized_command('install')
          svem = install_cmd.single_version_externally_managed
  
          return self.distribution.namespace_packages if svem else []
docs: Get namespace packages (list) but only for
          single_version_externally_managed installations and empty otherwise.