code: def _use_memcache(self, key, options=None):
      
      flag = ContextOptions.use_memcache(options)
      if flag is None:
        flag = self._memcache_policy(key)
      if flag is None:
        flag = ContextOptions.use_memcache(self._conn.config)
      if flag is None:
        flag = True
      return flag
docs: Return whether to use memcache for this key.
  
      Args:
        key: Key instance.
        options: ContextOptions instance, or None.
  
      Returns:
        True if the key should be cached in memcache, False otherwise.