code: def prune(self, root):
      
  
      max_entries_per_target = self._max_entries_per_target
      if os.path.isdir(root) and max_entries_per_target:
        safe_rm_oldest_items_in_dir(root, max_entries_per_target)
docs: Prune stale cache files
  
      If the option --cache-target-max-entry is greater than zero, then prune will remove all but n
      old cache files for each target/task.
  
      :param str root: The path under which cacheable artifacts will be cleaned