docs: public static String bytesToHex(byte[] raw) {
      if (raw == null) {
        return null;
      }
      final StringBuilder hex = new StringBuilder(2 * raw.length);
      for (final byte b : raw) {
        hex.append(Character.forDigit((b & 0xF0) >> 4, 16))
            .append(Character.forDigit((b & 0x0F), 16));
      }
      return hex.toString();
    }