code: @SuppressWarnings("OptionalGetWithoutIsPresent")
    public Token<DelegationTokenIdentifier> getBoundOrNewDT(String renewer) throws IOException {
      logger.atFine().log("Delegation token requested");
      if (isBoundToDT()) {
        // the FS was created on startup with a token, so return it.
        logger.atFine().log("Returning current token");
        return getBoundDT();
      }
  
      // not bound to a token, so create a new one.
      // issued DTs are not cached so that long-lived filesystems can
      // reliably issue session/role tokens.
      return tokenBinding.createDelegationToken(renewer);
    }
docs: Get any bound DT or create a new one.
  
  @return a delegation token.
  @throws IOException if one cannot be created