docs: private static byte[] decodePem(InputStream keyInputStream) throws IOException {
      BufferedReader reader = new BufferedReader(new InputStreamReader(keyInputStream));
      try {
        String line;
        while ((line = reader.readLine()) != null) {
          if (line.contains("-----BEGIN ")) {
            return readBytes(reader, line.trim().replace("BEGIN", "END"));
          }
        }
        throw new IOException("PEM is invalid: no begin marker");
      } finally {
        reader.close();
      }
    }