def update(self, client=None, unique_writer_identity=False):
        """API call:  update sink configuration via a PUT request

        See
        https://cloud.google.com/logging/docs/reference/v2/rest/v2/projects.sinks/update

        :type client: :class:`~google.cloud.logging.client.Client` or
                      ``NoneType``
        :param client: the client to use.  If not passed, falls back to the
                       ``client`` stored on the current sink.

        :type unique_writer_identity: bool
        :param unique_writer_identity: (Optional) determines the kind of
                                    IAM identity returned as
                                    writer_identity in the new sink.
        """
        client = self._require_client(client)
        resource = client.sinks_api.sink_update(
            self.project,
            self.name,
            self.filter_,
            self.destination,
            unique_writer_identity=unique_writer_identity,
        )
        self._update_from_api_repr(resource)