code: func (c *SDConfig) UnmarshalYAML(unmarshal func(interface{}) error) error {
  	*c = SDConfig{}
  	type plain SDConfig
  	err := unmarshal((*plain)(c))
  	if err != nil {
  		return err
  	}
  	if c.Role == "" {
  		return errors.Errorf("role missing (one of: pod, service, endpoints, node, ingress)")
  	}
  	err = c.HTTPClientConfig.Validate()
  	if err != nil {
  		return err
  	}
  	if c.APIServer.URL == nil && !reflect.DeepEqual(c.HTTPClientConfig, config_util.HTTPClientConfig{}) {
  		return errors.Errorf("to use custom HTTP client configuration please provide the 'api_server' URL explicitly")
  	}
  	return nil
  }
docs: // UnmarshalYAML implements the yaml.Unmarshaler interface.