def make_private(self, client=None):
        """Update blob's ACL, revoking read access for anonymous users.

        :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 blob's bucket.
        """
        self.acl.all().revoke_read()
        self.acl.save(client=client)