text: module.exports = (function () {
    const Type = require('./type');
    const _ = require('../utils');
  
    class _Undefined extends Type {
      constructor() {
        super(_Undefined, _.constant(true));
      }
  
      static validator(value) {
        if (!_.isExtends(this, Type)) throw new Error('Cannot call validator without binding this as instanceof class Type');
        return value === void 0;
      }
  
      static initializer() {
        if (!_.isExtends(this, Type)) throw new Error('Cannot call validator without binding this as instanceof class Type');
        return void 0;
      }
  
      toString() {
        return 'Undefined<Undefined>';
      }
    }
  
    return _Undefined;
  }());
  