问离子2，离子选择，让用户清除选择

EN

let alert = this.alertCtrl.create();
alert.setTitle('Lightsaber color');

alert.addInput({
  type: 'radio',
  label: 'Blue',
  value: 'blue',
  checked: true
});

alert.addInput({
  type: 'radio',
  label: 'Green',
  value: 'green'
});

alert.addButton('Cancel');
alert.addButton({
  text: 'Ok',
  handler: data => {
    console.log('Radio data:', data);
    this.testRadioOpen = false;
    this.testRadioResult = data;
  }
});

alert.present().then(() => {
  this.testRadioOpen = true;
});