docs: def current_batch(self):
          """Return the batch id for the tag.
  
          :return: :class: `int` current batch id
          """
          current_batch = memcache.get(self.group_key)
  
          if not current_batch:
              memcache.add(self.group_key, 1)
              current_batch = 1
  
          return current_batch