code: private static void savePrivateKeyPKCS1(OutputStream os, PrivateKey key)
      throws IllegalArgumentException, IOException {
  
      CertificateUtils.savePrivateKey(os, key, Encoding.PEM, null, new char[0],
        true);
  
    }
docs: Serializes a private key to an output stream following the pkcs1 encoding.
  
  This method just delegates to canl, but provides a much more understandable
  signature.
  
  @param os
  @param key
  @throws IllegalArgumentException
  @throws IOException