code: function URLRewriteStream(replacer) {
  
      if (typeof replacer !== "function") {
          throw new TypeError("Constructor expects a function as an argument.");
      }
  
      Transform.call(this, { objectMode: true });
  
      /**
       * The replacer function to use.
       * @type Function
       */
      this.replacer = replacer;
  
      /**
       * Any partial data that isn't ready to be returned yet.
       * @type *
       */
      this._leftover = "";
  }
docs: ------------------------------------------------------------------------------ Public ------------------------------------------------------------------------------ 
  Creates a new instance of a URL rewriter stream.
  @param {Function} replacer A function that receives each URL it comes across
  as a parameter and returns the URL to replace it with.
  @constructor