docs: private static Map<Object, Object> toProtoMap(@NullableDecl Object container) {
      if (container == null) {
        return Collections.emptyMap();
      }
      List<?> entryMessages = (List<?>) container;
  
      Map<Object, Object> retVal = Maps.newHashMap();
      for (Object entry : entryMessages) {
        Message message = (Message) entry;
        Object key = message.getAllFields().get(message.getDescriptorForType().findFieldByNumber(1));
        Object value =
            message.getAllFields().get(message.getDescriptorForType().findFieldByNumber(2));
        retVal.put(key, value);
      }
      return retVal;
    }