code: public static ByteString bytesDefaultValue(String bytes) {
      try {
        return ByteString.copyFrom(bytes.getBytes("ISO-8859-1"));
      } catch (UnsupportedEncodingException e) {
        // This should never happen since all JVMs are required to implement
        // ISO-8859-1.
        throw new IllegalStateException(
            "Java VM does not support a standard character set.", e);
      }
    }
docs: Helper called by generated code to construct default values for bytes
  fields.
  <p>
  This is a lot like {@link #stringDefaultValue}, but for bytes fields.
  In this case we only need the second of the two hacks -- allowing us to
  embed raw bytes as a string literal with ISO-8859-1 encoding.