code: def set_disk_usage(self, total_size, path=None):
          
          if path is None:
              path = self.root.name
          mount_point = self._mount_point_for_path(path)
          if (mount_point['total_size'] is not None and
                  mount_point['used_size'] > total_size):
              self.raise_io_error(errno.ENOSPC, path)
          mount_point['total_size'] = total_size
docs: Changes the total size of the file system, preserving the used space.
          Example usage: set the size of an auto-mounted Windows drive.
  
          Args:
              total_size: The new total size of the filesystem in bytes.
  
              path: The disk space is changed for the file system device where
                  `path` resides.
                  Defaults to the root path (e.g. '/' on Unix systems).
  
          Raises:
              IOError: if the new space is smaller than the used size.