code: public static void readStartObjectToken(JsonParser jsonParser,
                                            String parentFieldName)
      throws IOException {
      readToken(jsonParser, parentFieldName, JsonToken.START_OBJECT);
    }
docs: This is a helper method that reads a JSON token using a JsonParser
  instance, and throws an exception if the next token is not START_OBJECT.
  
  @param jsonParser The JsonParser instance to be used
  @param parentFieldName The name of the field
  @throws IOException