code: func Errorf(format string, args ...interface{}) {
  	var s string
  	if len(args) > 0 {
  		s = fmt.Sprintf(format, args...)
  	} else {
  		s = format
  	}
  	klog.ErrorDepth(1, fmt.Sprintf(logFmt, s))
  }
docs: // Errorf shim that inserts "kubelet config controller" at the beginning of the log message,
  // while still reporting the call site of the logging function.