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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def save_predefined(self, predefined, client=None):
 """Save this ACL for the current bucket using a predefined ACL. If :attr:`user_project` is set, bills the API request to that project. :type predefined: str :param predefined: An identifier for a predefined ACL. Must be one of the keys in :attr:`PREDEFINED_JSON_ACLS` or :attr:`PREDEFINED_XML_ACLS` (which will be aliased to the corresponding JSON name). If passed, `acl` must be None. :type client: :class:`~google.cloud.storage.client.Client` or ``NoneType`` :param client: Optional. The client to use. If not passed, falls back to the ``client`` stored on the ACL's parent. """

        predefined = self.validate_predefined(predefined)
        self._save(None, predefined, client)