def patch(self, client=None):
        """Sends all changed properties in a PATCH request.

        Updates the ``_properties`` with the response from the backend.

        If :attr:`user_project` is set, bills the API request to that project.

        :type client: :class:`~google.cloud.storage.client.Client` or
                      ``NoneType``
        :param client: the client to use.  If not passed, falls back to the
                       ``client`` stored on the current object.
        """
        # Special case: For buckets, it is possible that labels are being
        # removed; this requires special handling.
        if self._label_removals:
            self._changes.add("labels")
            self._properties.setdefault("labels", {})
            for removed_label in self._label_removals:
                self._properties["labels"][removed_label] = None

        # Call the superclass method.
        return super(Bucket, self).patch(client=client)