code: def _get_item_cache(self, item):
          
          cache = self._item_cache
          res = cache.get(item)
          if res is None:
              values = self._data.get(item)
              res = self._box_item_values(item, values)
              cache[item] = res
              res._set_as_cached(item, self)
  
              # for a chain
              res._is_copy = self._is_copy
          return res
docs: Return the cached item, item represents a label indexer.