code: def from_stored(self, key):
          
          # only one stored key allowed
          if self.stored_key:
              raise ValueError('This collection is already based on a stored one')
  
          # prepare the collection
          self.stored_key = key
          self.intersect(_StoredCollection(self.cls.get_connection(), key))
          self.sort(by='nosort')  # keep stored order
  
          # count the number of results to manage empty result (to not behave like
          # expired key)
          self._stored_len = self.cls.get_connection().llen(key)
  
          return self
docs: Set the current collection as based on a stored one. The key argument
          is the key off the stored collection.