code: @Nonnull
      public static <Message extends PMessage<Message, Field>, Field extends PField>
      String debugString(Message message) {
          ByteArrayOutputStream baos = new ByteArrayOutputStream();
          DEBUG_STRING_SERIALIZER.serialize(baos, message);
          return new String(baos.toByteArray(), UTF_8);
      }
docs: Prints a pretty formatted string that is optimized for diffing (mainly
  for testing and debugging).
  
  @param message The message to stringify.
  @param <Message> The message type.
  @param <Field> The message field type.
  @return The resulting string.