code: function throughWithCallback(onData) {
  
    return through.obj(function (chunk, enc, next) {
  
      if (onData) {
        onData(null, chunk);
      }
  
      next(null, chunk);
    });
  }
docs: Create a through stream that simply calls a callback with the contents.
  Make sure to also pass the data along so the stream continues.
  
  @private
  @static
  @since    1.3.0
  @category Utilities
  
  @param    {Function}  onData - Callback with an error or parsed JSON.
  @returns  {Stream}           - Transform Stream