code: func readConfig(config io.Reader) *pluginConfig {
  	defaultConfig := &pluginConfig{}
  	if config == nil || reflect.ValueOf(config).IsNil() {
  		return defaultConfig
  	}
  	d := yaml.NewYAMLOrJSONDecoder(config, 4096)
  	for {
  		if err := d.Decode(defaultConfig); err != nil {
  			if err != io.EOF {
  				continue
  			}
  		}
  		break
  	}
  	return defaultConfig
  }
docs: // readConfig reads default value of clusterDefaultNodeSelector
  // from the file provided with --admission-control-config-file
  // If the file is not supplied, it defaults to ""
  // The format in a file:
  // podNodeSelectorPluginConfig:
  //  clusterDefaultNodeSelector: <node-selectors-labels>
  //  namespace1: <node-selectors-labels>
  //  namespace2: <node-selectors-labels>