code: def associate(base_dir: str, rr_id: str, tails_hash: str) -> None:
          
  
          LOGGER.debug('Tails.associate >>> base_dir: %s, rr_id: %s, tails_hash: %s', base_dir, rr_id, tails_hash)
  
          if not ok_rev_reg_id(rr_id):
              LOGGER.debug('Tails.associate <!< Bad rev reg id %s', rr_id)
              raise BadIdentifier('Bad rev reg id {}'.format(rr_id))
  
          if not Tails.ok_hash(tails_hash):
              LOGGER.debug('Tails.associate <!< Bad tails hash %s', tails_hash)
              raise BadIdentifier('Bad tails hash {}'.format(tails_hash))
  
          cd_id = rev_reg_id2cred_def_id(rr_id)
          directory = join(base_dir, cd_id)
          cwd = getcwd()
          makedirs(directory, exist_ok=True)
          chdir(directory)
          symlink(tails_hash, rr_id)
          chdir(cwd)
  
          LOGGER.debug('Tails.associate <<<')
docs: Create symbolic link to tails file named tails_hash for rev reg id rr_id.
  
          :param rr_id: rev reg id
          :param tails_hash: hash of tails file, serving as file name