func (l *Logger) Warnf(format string, args ...interface{}) {
	l.Output(2, LevelWarn, fmt.Sprintf(format, args...))
}
func (l *Logger) Warnf(format string, args ...interface{}) {
	l.Output(2, LevelWarn, fmt.Sprintf(format, args...))
}
func ( l * Logger ) Warnf ( format string , args ... interface { } ) { l . Output ( 2 , LevelWarn , fmt . Sprintf ( format , args ... ) ) }
// Warnf records the log with warn level
Warnf records the log with warn level