Backup method driver.

def backup(self, paths=None):
        """Backup method driver."""
        if not paths:
            paths = self._get_paths()

        try:
            self._backup_compresslevel(paths)
        except TypeError:
            try:
                self._backup_pb_gui(paths)
            except ImportError:
                self._backup_pb_tqdm(paths)

        # Delete source if specified
        if self.delete_source:
            shutil.rmtree(self.source)
        return self.zip_filename