code: func (plugin *kubenetNetworkPlugin) checkRequiredCNIPlugins() bool {
  	for _, dir := range plugin.binDirs {
  		if plugin.checkRequiredCNIPluginsInOneDir(dir) {
  			return true
  		}
  	}
  	return false
  }
docs: // checkRequiredCNIPlugins returns if all kubenet required cni plugins can be found at /opt/cni/bin or user specified NetworkPluginDir.