code: def pretty_print_config_to_json(self, configs):
      
      descriptor = self.get_directory_list_doc(configs)
      return json.dumps(descriptor, sort_keys=True, indent=2,
                        separators=(',', ': '))
docs: JSON string description of a protorpc.remote.Service in a discovery doc.
  
      Args:
        configs: Either a single dict or a list of dicts containing the service
          configurations to list.
  
      Returns:
        string, The directory list document as a JSON string.