code: def gets(self, key):
          
          for server in self.servers:
              value, cas = server.get(key)
              if value is not None:
                  return value, cas
          return None, None
docs: Get a key from server, returning the value and its CAS key.
  
          This method is for API compatibility with other implementations.
  
          :param key: Key's name
          :type key: six.string_types
          :return: Returns (key data, value), or (None, None) if the value is not in cache.
          :rtype: object