public Errors groupLevelError(String groupId) {
        if (error != null) {
            return error;
        }
        return groupLevelErrors.get(groupId);
    }
Constructor with throttle time for version 8 and above.
@param throttleTimeMs The time in milliseconds that this response was throttled
@param errors Potential coordinator or group level error code
@param responseData Fetched offset information grouped by topic-partition and by group
clients/src/main/java/org/apache/kafka/common/requests/OffsetFetchResponse.java