code: private String parseDefaultValue(String key) throws IOException {
          jsonParser.nextToken();
          String value = null;
          JsonToken currentToken = jsonParser.getCurrentToken();
          if (currentToken != JsonToken.VALUE_NULL) {
              if (currentToken == JsonToken.START_ARRAY || currentToken == JsonToken.START_OBJECT) {
                  JsonNode node = jsonParser.readValueAsTree();
                  value = node.toString();
              } else {
                  value = jsonParser.getValueAsString();
              }
          }
          return value;
      }
docs: Parses the event with key as default value.
  
  If the value is JSON null, then we will return null.
  If the value is JSON object (of starting with START_ARRAY or START_OBject) , then we will convert the object to String.
  If the value is JSON scalar value (non-structured object), then we will return simply return it as String.
  
  @param key
  @throws IOException