Forget about the changes

def cancel(self):
        """
        Forget about the changes
        """
        logger.info("Index: Index update cancelled")
        if self.index_writer:
            self.index_writer.cancel()
            del self.index_writer
        self.index_writer = None
        if self.label_guesser_updater:
            self.label_guesser_updater.cancel()
        self.label_guesser_updater = None