docs: def clean(self, suffixes=None):
          """
          Remove all persistence-related files from the directory.
          """
          if suffixes is None:
              suffixes = [DONE_SUFFIX, LOCK_SUFFIX, PART_SUFFIX]
  
          for suffix in suffixes:
              listing = self.working_context.get_listing(suffix)
              for filename in listing:
                  self.working_context.remove(filename)