code: func (plugin *kubenetNetworkPlugin) checkRequiredCNIPluginsInOneDir(dir string) bool {
  	files, err := ioutil.ReadDir(dir)
  	if err != nil {
  		return false
  	}
  	for _, cniPlugin := range requiredCNIPlugins {
  		found := false
  		for _, file := range files {
  			if strings.TrimSpace(file.Name()) == cniPlugin {
  				found = true
  				break
  			}
  		}
  		if !found {
  			return false
  		}
  	}
  	return true
  }
docs: // checkRequiredCNIPluginsInOneDir returns true if all required cni plugins are placed in dir