Array.prototype.concatAll = function() {
	var results = [];
	this.forEach(subArray => {
    subArray.forEach(item => {
                     results.push(item);
  });
		// ------------ INSERT CODE HERE! ----------------------------
		// Add all the items in each subArray to the results array.
		// ------------ INSERT CODE HERE! ----------------------------
	});

	return results;
};

 /*
  return movieLists.map(function(genre) {
    return genre.videos.map(function(video) {
      return video.id;
    });
  }).concatAll();
  */
  // I stupidly left out a paren
  return movieLists.map(genre => genre.videos.map(video => video.id)).concatAll();