code: func (a *AuthenticationConfig) Parse() (services.AuthPreference, services.OIDCConnector, error) {
  	var err error
  
  	var u services.U2F
  	if a.U2F != nil {
  		u = a.U2F.Parse()
  	}
  
  	ap, err := services.NewAuthPreference(services.AuthPreferenceSpecV2{
  		Type:          a.Type,
  		SecondFactor:  a.SecondFactor,
  		ConnectorName: a.ConnectorName,
  		U2F:           &u,
  	})
  	if err != nil {
  		return nil, nil, trace.Wrap(err)
  	}
  	// check to make sure the configuration is valid
  	err = ap.CheckAndSetDefaults()
  	if err != nil {
  		return nil, nil, trace.Wrap(err)
  	}
  
  	var oidcConnector services.OIDCConnector
  	if a.OIDC != nil {
  		oidcConnector, err = a.OIDC.Parse()
  		if err != nil {
  			return nil, nil, trace.Wrap(err)
  		}
  	}
  
  	return ap, oidcConnector, nil
  }
docs: // Parse returns the Authentication Configuration in two parts: AuthPreference
  // (type, second factor, u2f) and OIDCConnector.