src/vs/platform/log/common/fileLog.ts/FileLogger/stringifyLogLevel
class FileLogger:	private stringifyLogLevel(level: LogLevel): string {
		switch (level) {
			case LogLevel.Debug: return 'debug';
			case LogLevel.Error: return 'error';
			case LogLevel.Info: return 'info';
			case LogLevel.Trace: return 'trace';
			case LogLevel.Warning: return 'warning';
		}
		return '';
	}