code: function Prompt() {
    Base.apply(this, arguments);
  
    var rawDefault = true;
  
    utils.extend(this.opt, {
      filter: function(input) {
        var value = rawDefault;
        if (input != null && input !== '') {
          value = /^y(es)?/i.test(input);
        }
        return value;
      }.bind(this)
    });
  
    if (typeof this.opt.default === 'boolean') {
      rawDefault = this.opt.default;
    }
  
    this.opt.default = rawDefault ? 'Y/n' : 'y/N';
  
    return this;
  }
docs: Constructor