code: function Radio(/*question, answers, rl*/) {
    debug('initializing from <%s>', __filename);
    Checkbox.apply(this, arguments);
    this.question.type = 'radio';
  
    this.action('i', function(pos) {
      return pos;
    });
  
    this.action('a', function(pos) {
      return pos;
    });
  
    this.action('number', function(pos, key) {
      return enable(this, pos, key);
    });
  
    this.action('space', function(pos) {
      return enable(this, pos);
    });
  
    function enable(actions, pos, key) {
      pos = actions.position(pos, key) + (key ? -1 : 0);
      actions.choices.uncheck();
      actions.choices.check(pos);
      return pos;
    }
  }
docs: Radio prompt