code: def clean_extra(self):
          
          extra_paths = self.get_extra_paths()
          for path in extra_paths:
              if not os.path.exists(path):
                  continue
              if os.path.isdir(path):
                  self._clean_directory(path)
              else:
                  self._clean_file(path)
docs: Clean extra files/directories specified by get_extra_paths()