text: const stream = require('stream');
  const util = require('util');
  
  const Duplex = stream.Duplex;
  
  function DuplexStream(options) {
  	if (!(this instanceof DuplexStream)) {
  		return new DuplexStream(options);
  	}
  	Duplex.call(this, options);
  }
  util.inherits(DuplexStream, Duplex);
  
  DuplexStream.prototype._write = function (chunk, enc, cb) {
  	this.push(chunk);
  	cb();
  };
  
  
  DuplexStream.prototype._read = function (n) {
  
  };
  
  module.exports = DuplexStream;