How to use the react-native-nfc-manager.start function in react-native-nfc-manager

_startNfc = () => {
    NfcManager.start()
      .then(() => NfcManager.isEnabled())
      .then(enabled => this.setState({ enabled }))
      .catch(err => {
        console.warn(err);
        this.setState({ enabled: false });
      });
  };

_startNfc() {
        NfcManager.start({
            onSessionClosedIOS: () => {
                console.log('ios session closed');
            }
        })
            .then(result => {
                console.log('start OK', result);
            })
            .catch(error => {
                console.warn('start fail', error);
                this.setState({supported: false});
            })

        if (Platform.OS === 'android') {
            NfcManager.getLaunchTagEvent()
                .then(tag => {
                    console.log('launch tag', tag);

_startNfc = () => {
        NfcManager.start()
            .then(() => NfcManager.isEnabled())
            .then(enabled => this.setState({enabled}))
            .catch(err => {
                console.warn(err);
                this.setState({enabled: false})
            })
    }