code: async def stop(wallet_name: str) -> None:
          
  
          LOGGER.debug('RevRegBuilder.stop >>>')
  
          dir_sentinel = join(RevRegBuilder.dir_tails_sentinel(wallet_name))
  
          if isdir(dir_sentinel):
              open(join(dir_sentinel, '.stop'), 'w').close()  # touch
  
              while any(isfile(join(dir_sentinel, d, '.in-progress')) for d in listdir(dir_sentinel)):
                  await asyncio.sleep(1)
  
          LOGGER.debug('RevRegBuilder.stop <<<')
docs: Gracefully stop an external revocation registry builder, waiting for its current.
  
          The indy-sdk toolkit uses a temporary directory for tails file mustration,
          and shutting down the toolkit removes the directory, crashing the external
          tails file write. This method allows a graceful stop to wait for completion
          of such tasks already in progress.
  
          :wallet_name: name external revocation registry builder to check
          :return: whether a task is pending.