code: func (l *Logger) Errorf(format string, v ...interface{}) {
  	if l.getLevel() <= Error {
  		l.getHandler().Log(l.name, Error, fmt.Sprintf(format, v...), 1)
  	}
  }
docs: // Errorf logs a format string with values if the logger's level is error or
  // even more permissive.