code: async def get_files_to_delete(self) -> List[str]:
          
          dir_name, base_name = os.path.split(self.absolute_file_path)
          file_names = await self.loop.run_in_executor(
              None, lambda: os.listdir(dir_name)
          )
          result = []
          prefix = base_name + "."
          plen = len(prefix)
          for file_name in file_names:
              if file_name[:plen] == prefix:
                  suffix = file_name[plen:]
                  if self.ext_match.match(suffix):
                      result.append(os.path.join(dir_name, file_name))
          if len(result) < self.backup_count:
              return []
          else:
              return result[: len(result) - self.backup_count]
docs: Determine the files to delete when rolling over.