code: private Map<String, Object> readObjectArgument(JsonReader jsonReader)
              throws IOException {
          Map<String, Object> arg = new LinkedHashMap<>();
          jsonReader.beginObject();
          while (jsonReader.hasNext()) {
              arg.put(jsonReader.nextName(),
                      JsonParser.GSON.fromJson(jsonReader, Object.class));
          }
          jsonReader.endObject();
          return arg;
      }
docs: Reads a generic object argument from the given JsonReader.
  
  @param jsonReader JsonReader expecting an object next
  @return Map representing a generic object argument