code: def contains(self, key):
      '''Returns whether the object named by `key` exists.
         First checks ``cache_datastore``.
      '''
      return self.cache_datastore.contains(key) \
          or self.child_datastore.contains(keyf contains(self, key):
      '''Returns whether the object named by `key` exists.
         First checks ``cache_datastore``.
      '''
      return self.cache_datastore.contains(key) \
          or self.child_datastore.contains(key)
docs: Returns whether the object named by `key` exists.
         First checks ``cache_datastore``.