I want to add new level critical for log of winston-daily-rotate-file.

I declare critical: LeveledLogMethod; in class Logger extends NodeJSStream.Transform of index.d.ts of winston/index.d.ts.

In logger.ts of my application, I create a function critical and return FLLogger.getInstance().logger.critical(fullMessage, error); in it.

However, I receive an message that FLLogger.getInstance(...).logger.critical is not a function..

Here is my code in logger.ts

public static critical(fileName: string, methodName: string, message: string, errorCode: string, error?: any) {
    const fullMessage = `[CODE: ${errorCode}] [FILE: ${fileName}] [METHOD: ${methodName}] [Host IP: ${this.getHostIP()}] ${message}: `;
    FLLogger.getInstance().logger.critical(fullMessage, error);
}

public static init() {
    FLLogger.getInstance().logger = createLogger({
        format: format.combine(
            format.timestamp({ format: 'YYYY-MM-DD HH:mm:ss.SSS' }), // Customize timestamp format
            format.errors({ stack: true }), // Include errors if any
            format.prettyPrint(),
            format.printf((info) => `[${info.timestamp}] [${info.level.toUpperCase()}] ${info.message}.`,
            ),
        ),
        transports: [
            new transports.Console(),
            new transports.DailyRotateFile({
                dirname: `/${Constants.LOG_FOLDER_NAME}`,
                filename: 'app-%DATE%-critical.log',
                datePattern: 'YYYY-MM-DD',
                zippedArchive: true, // archive log files for backup
                maxSize: '10m', // Log file size
                maxFiles: '30d', // Delete log file in 30 days
                level: 'critical',
            }),
        ],
    });
}

How to fix it? Does I miss something and please explain me why?