@Override
    public String toString() {
        return "InLongMsgHead{"
                + "attributes=" + attributes
                + ", streamId='" + streamId + '\''
                + ", time=" + time
                + ", predefinedFields=" + predefinedFields
                + '}';
    }
The predefined fields extracted from the head.
inlong-sort/sort-formats/format-common/src/main/java/org/apache/inlong/sort/formats/inlongmsg/InLongMsgHead.java