docs: def _extract_tag_value(self, entity, tag_name):
          """Extra tag information from the API result (containers or images).
          Cache extracted tags inside the entity object.
          """
          if tag_name not in TAG_EXTRACTORS:
              self.warning("{0} isn't a supported tag".format(tag_name))
              return
  
          # Check for already extracted tags
          if "_tag_values" not in entity:
              entity["_tag_values"] = {}
  
          if tag_name not in entity["_tag_values"]:
              entity["_tag_values"][tag_name] = TAG_EXTRACTORS[tag_name](entity)
  
          return entity["_tag_values"][tag_name]